Planning and facilitation systems and methods for cryosurgery

ABSTRACT

Systems and methods for planning a cryoablation procedure and for facilitating a cryoablation procedure utilize integrated images displaying, in a common virtual space, a three-dimensional model of a surgical intervention site based on digitized preparatory images of the site from first imaging modalities, simulation images of cryoprobes used according to an operator-planned cryoablation procedure at the site, and real-time images provided by second imaging modalities during cryoablation. The system supplies recommendations for and evaluations of the planned cryoablation procedure, feedback to an operator during cryoablation, and guidance and control signals for operating a cryosurgery tool during cryoablation. Methods are provided for generating a nearly-uniform cold field among a plurality of cryoprobes, for cryoablating a volume with smooth and well-defined borders, thereby minimizing damage to healthy tissues.

[0001] This application claims the benefir of priority from U.S.Provisional Patent Application No. 60/221,891, filed Jul. 31, 2000.

FIELD AND BACKGROUND OF THE INVENTION

[0002] The present invention relates to cryosurgical systems and methodsuseable for planning and for facilitating a cryoablation procedure. Moreparticularly, the present invention relates to the use of integratedimages displaying, in a common virtual space, images of athree-dimensional model of a surgical intervention site, simulationimages of a planned cryoablation procedure at the site, and real-timeimages of the site during cryoablation. The present invention furtherrelates to system-supplied recommendations for, and evaluations of, aplanned cryoablation procedure, and to system-supplied feedback to anoperator and system-supplied control signals to a cryosurgery toolduring cryoablation.

[0003] Cryosurgical procedures involve deep tissue freezing whichresults in tissue destruction due to rupture of cells and or cellorganelles within the tissue. Deep tissue freezing is effected byinsertion of a tip of a cryosurgical device into the tissue, eithertransperineally, endoscopically or laparoscopically, and a formation of,what is known in the art as, an ice-ball around the tip.

[0004] In order to effectively destroy a tissue by such an ice-ball, thediameter of the ball should be substantially larger than the region ofthe tissue to be treated, which constraint derives from the specificprofile of temperature distribution across the ice-ball.

[0005] Specifically, the temperature required for effectively destroyinga tissue is about −40° C., or cooler. However, the temperature at thesurface of the ice-ball is 0° C. The temperature declines exponentiallytowards the center of the ball such that an isothermal surface of about−40° C. is typically located within the ice-ball substantially at thehalf way between the center of the ball and its surface.

[0006] Thus, in order to effectively destroy a tissue there is a need tolocate the isothermal surface of −40° C. at the periphery of the treatedtissue, thereby exposing adjacent, usually healthy, tissues to theexternal portions of the ice-ball. The application of temperatures ofbetween about −40° C. and 0° C. to such healthy tissues usually causessubstantial damage thereto, which damage may result in temporary orpermanent impairment of functional organs.

[0007] In addition, when the adjacent tissues are present at oppositeborders with respect to the freeze treated tissue, such as in the caseof prostate freeze treatments, as is further detailed below, and sincethe growth of the ice-ball is in substantially similar rate in alldirections toward its periphery, if the tip of the cryosurgical deviceis not precisely centered, the ice-ball reaches one of the bordersbefore it reaches the other border, and decision making of whether tocontinue the process of freezing, risking a damage to close healthytissues, or to halt the process of freezing, risking a non-completedestruction of the treated tissue, must be made.

[0008] Although the present invention is applicable to any cryosurgicaltreatment, discussion is hereinafter primarily focused on a cryosurgicaltreatment of a patient's prostate.

[0009] Thus, when treating a tumor located at a patient's prostate,there is a trade-of between two options: (a) effectively destroying theprostatic tissue extending between the prostatic urethra and theperiphery of the prostate and causing unavoidable damage to thepatient's urethra or organs adjacent the prostate such as the rectum andnerves; (b) avoiding the damaging of the prostatic urethra and adjacentorgans, but exposing the patient to the risk of malignancy due toineffective destruction of the prostate tumor. Treatment of benignprostate hyperplasia (BPH), while not requiring total destruction of anentire volume of prostate tissue as does treatment of a malignancy,nevertheless does run the risk of causing damage to healthy functionaltissues and organs adjacent to the prostate, if care is not taken tolimit the scope of destructive freezing to appropriate locations.

[0010] A classical cryosurgery procedure for treating the prostateincludes the introduction of 5-7 probes into the prostate, the probesbeing typically arranged around the prostatic urethra such that a singleprobe is located, preferably centered, between the prostatic urethra andthe periphery of the prostate. The dimensions of such a single probe areusually adapted for effectively treating the prostatic tissue segmentextending from the urethra to the periphery of the prostate, e.g., a tipof 3 millimeters in diameter, generating an ice-ball of 3-4 centimetersin diameter, depending on the size of the prostate. Since a singleice-ball is used for freezing such a prostatic tissue segment, thevolume of adjacent tissues exposed to damage is substantially greaterthan the volume of the treated tissue. For example, if the area of theice-ball in cross section is πR², and an effective treatment of at least−40° C. is provided to an area of π(R/2)² (in cross section), then thearea of adjacent tissues (in cross section) exposed to between about−40° C. and about 0° C. is πR²−0.25(πR²)=0.75(πR²), which is three timesthe area of the tissue effectively treated by the ice-ball.

[0011] A modification of the classic cryosurgery procedure described inthe preceding paragraph, intended to avoid excessive damage to adjacenttissues, is to use such a single probe of a smaller diameter producingan ice-ball of smaller size. Such a modification, however, exposes thepatient to the danger of malignancy because of a possible incompletedestruction of the tumor.

[0012] The classical cryosurgery procedure herein described, therefore,does not provide effective resolution of treatment along the planesperpendicular to the axis of penetration of the cryosurgical probe intothe patient's organ.

[0013] A further limitation of the classical procedure stems from thefact that anatomical organs such as the prostate usually feature anasymmetric three-dimensional shape. Consequently, introduction of acryosurgical probe along a specific path of penetration within the organmay provide effective treatment to specific regions located at specificdepths of penetration but at the same time may severely damage otherportions of the organ located at other depths of penetration.

[0014] U.S. Pat. No. 6,142,991 to Schatzberger teaches a high resolutioncryosurgical method and device for treating a patient's prostatedesigned to overcome the described limitations of the classicalcryosurgery procedure described hereinabove. Schatzberger's “highresolution” method (referred to as the “HR method” hereinbelow)comprises the steps of (a) introducing a plurality of cryosurgicalprobes to the prostate, the probes having a substantially small diameterand are distributed across the prostate, so as to form an outerarrangement of probes adjacent the periphery of the prostate and aninner arrangement of probes adjacent the prostatic urethra; and (b)producing an ice-ball at the end of each of said cryosurgical probes, soas to locally freeze a tissue segment of the prostate. Schatzberger'sapparatus (referred to hereinbelow as the “HR” apparatus) comprises (a)a plurality of cryosurgical probes of small diameter, the probes servefor insertion into the patient's organ, the probes being for producingice-balls for locally freezing selected portions of the organ; (b) aguiding element including a net of apertures for inserting thecryosurgical probes therethrough; and (c) an imaging device forproviding a set of images, the images being for providing information onspecific planes located at specific depths within the organ, each ofsaid images including a net of marks being correlated to the net ofapertures of the guiding element, wherein the marks represent thelocations of ice-balls which may be formed by the cryosurgical probeswhen introduced through said apertures of the guiding element to saiddistinct depths within the organ.

[0015] The HR method and device provide the advantages of highresolution of treatment along the axis of penetration of thecryosurgical probe into the patient's organ as well as along the planesperpendicular to the axis of penetration, thereby enabling toeffectively destroy selective portions of a patient's tissue whileminimizing damage to adjacent tissues and organs, and to selectivelytreat various portions of the tissue located at different depths of theorgan, thereby effectively freezing selected portions of the tissuewhile avoiding the damaging of other tissues and organs located at otherdepth along the axis of penetration.

[0016] Schatzberger, in U.S. Pat. No. 6,142,991 also teaches theadditional step of three dimensionally mapping an organ of a patient soas to form a three dimensional grid thereof, and applying a multi-probesystem introduced into the organ according to the grid, so as to enablesystematic high-resolution three dimensional cryosurgical treatment ofthe organ and selective destruction of the treated tissue with minimaldamage to surrounding, healthy, tissues.

[0017] It is, however, a disadvantage of the HR apparatus and method astaught in U.S. Pat. No. 6,142,991 that the apparatus enables, and themethod requires, a high level of diagnostic sophistication in theselection and definition of the particular volume of tissue to becryoablated. Real-time imaging capabilities of the HR apparatus providefor imaging of the target organ at a selected depth of penetration andthereby assist an operator in deciding where to introduce and utilize aplurality of cryogenic probes, yet the complex three-dimensionalgeometry of the cryoablation target is poorly rendered by the set of twodimensional images constituting the three dimensional grid ascontemplated by the HR method and apparatus. In this prior art method,little assistance is provided for an operator in understanding the threedimensional shape and structure of the cryoablation target and thesurrounding tissues. Information vital to the operator may be present inthe set of images, yet difficult for the operator to see and appreciate.In a set of images of this type, the details may be present, yet it maybe difficult to appreciate their significance because of the difficultyof seeing them in context. A three dimensional “grid” composed of aplurality of two dimensional images such as ultrasound images containmany details, yet do not facilitate the understanding of those detailsin a three dimensional context.

[0018] Thus there is a widely recognized need for, and it would behighly advantageous to have, an apparatus for facilitating cryosurgerywhich provides real-time imaging of a cryoablation target site in amanner which is easy for an operator to visualize and to understand.

[0019] It is an additional limitation of the HR method and apparatus,and of other prior art systems, that the imaging capabilitiescontemplated are not well adapted to assist an operator in planning acryoablation procedure. In addition to the fact that the imagingfacilities there provided are poorly adapted to visualization of thethree dimensional space by an operator, they are also limited in thatthe apparatus is poorly adapted to providing images of the target areain advance of the operation, e.g., for planning purposes. The describedHR equipment might, of course, but used to create the described threedimensional mapping of the target area well in advance of a surgicalintervention, but no mechanism is provided for facilitating the relatingthe images so obtained, and any planned procedures based on thoseimages, to a subsequent intervention procedure. Moreover, the fact thatthe imaging modality of the HR apparatus is physically connected toparts of the cryosurgery equipment limits its versatility and may insome cases make it awkward to use for creating preparatory images of anintervention site.

[0020] Thus there is a widely recognized need for, and it would behighly advantageous to have, an apparatus for planning and forfacilitating cryosurgery which provides easily understandablevisualization of a cryoablation target site in advance of a surgicalintervention, which further provides facilities for studying the siteand for planning the intervention, and which yet further providesfacilities for applying information gleaned from prior study of theimaged site, and specific plans for intervening in the site, to theactual site, in real time, during the planned cryoablation operation.

[0021] It is a further limitation of the HR method that no means areprovided for facilitating the relating of images obtained in advance ofa surgical intervention to a subsequent intervention. Yet whereasultrasound images of a target site can be generated in real time duringan intervention, and MRI techniques may also (if somewhat less easily)also be obtained during cryosurgery, other imaging techniques (CT scans,for example) are less well adapted to being produced during the courseof an actual cryosurgery intervention.

[0022] Thus there is a widely recognized need for, and it would behighly advantageous to have, an apparatus and method for facilitatingthe relating of images obtained prior surgery to real-time images, fromthe same or from additional sources, obtained during cryosurgery.

[0023] Much is now known about the tissue-destructive processes ofcryoablation, and about the subsequent short-term and long-termconsequences to an organ such as a prostate which has undergone partialcryoablation. The laws of physics relating to the conduction of heat ina body, reinforced by experimentation and further reinforced byaccumulated clinical experience in cryosurgery, provide a wealth ofinformation enabling to predict with some accuracy the effect of aspecific planned cryoablation procedure on target tissues. Thisinformation, and this capability for prediction, is underutilized incurrent cryosurgery practice.

[0024] The SEEDNET TRAINING AND PLANNING SOFTWARE (“STPS”) marketed byGalil Medical Ltd. of Yokneam, Israel constitutes a set in thisdirection, in that it provides a system for displaying, and allowing anoperator to manipulate, a three-dimensional model of a prostate, andfurther allows an operator to plan a cryoablation intervention and tovisualize the predicted effect of that planned intervention on theprostate tissues. STPS, however, is limited in that it does not providemeans for relating a preliminary three dimensional model of a prostateto the prostate as revealed in real-time during the course of a surgicalprocedure. Moreover, the predictive ability of the STPS system islimited to predicting the extent of the freezing produced by a givendeployment of a plurality of cryoprobes over a given time. No assistanceis provided to an operator in discerning interactions between thepredicted cryoablation and specific structures desired to be protectedor to be destroyed. No assistance is given in predicting long-termeffects of a given cryoablation procedure. No assistance is given inrecommending procedures, placement of probes, temperature, or timing ofan intervention.

[0025] Thus there is a widely recognized need for, and it would behighly advantageous to have, apparatus and method for calculatingprobable immediate, short-term, and long-term effects of a plannedcryoablation procedure, thereby to facilitate the planning of such aprocedure. There is further a widely recognized need for, and it wouldbe highly advantageous to have, apparatus and method for facilitatingthe implementation of such a planned procedure, in real time, duringexecution of a planned cryoablation.

[0026] It is noted that with respect to BPH, the need for such aplanning and facilitation apparatus is particularly strong.

[0027] BPH, which affects a large number of adult men, is anon-cancerous enlargement of the prostate. BPH frequently results in agradual squeezing of the portion of the urethra which traverses theprostate, also known as the prostatic urethra. This causes patients toexperience a frequent urge to urinate because of incomplete emptying ofthe bladder and a burning sensation or similar discomfort duringurination. The obstruction of urinary flow can also lead to a generallack of control over urination, including difficulty initiatingurination when desired, as well as difficulty in preventing urinary flowbecause of the residual volume of urine in the bladder, a conditionknown as urinary incontinence. Left untreated, the obstruction caused byBPH can lead to acute urinary retention (complete inability to urinate),serious urinary tract infections and permanent bladder and kidneydamage.

[0028] Most males will eventually suffer from BPH. The incidence of BPHfor men in their fifties is approximately 50% and rises to approximately80% by the age of 80. The general aging of the United States population,as well as increasing life expectancies, is anticipated to contribute tothe continued growth in the number of BPH sufferers.

[0029] Patients diagnosed with BPH generally have several options fortreatment: watchful waiting, drug therapy, surgical intervention,including transurethral resection of the prostate (TURP), laser assistedprostatectomy and new less invasive thermal therapies.

[0030] Various disadvantages of existing therapies have limited thenumber of patients suffering from BPH who are actually treated. In 1999,the number of patients actually treated by surgical approaches wasestimated to be 2% to 3%. Treatment is generally reserved for patientswith intolerable symptoms or those with significant potential symptomsif treatment is withheld. A large number of the BPH patients delaydiscussing their symptoms or elect “watchful waiting” to see if thecondition remains tolerable.

[0031] Thus, development of a less invasive, more convenient, or moresuccessful treatment for BPH could result in a substantial increase inthe number of BPH patients who elect to receive interventional therapy.

[0032] Cryoablation is a candidate for being such a popularizetreatment.

[0033] With respect to drug therapies: some drugs are designed to shrinkthe prostate by inhibiting or slowing the growth of prostate cells.Other drugs are designed to relax the muscles in the prostate andbladder neck to relieve urethral obstruction. Current drug therapygenerally requires daily administration for the duration of thepatient's life.

[0034] With respect to surgical interventions: the most common surgicalprocedure, transurethral resection of the prostate (TURP), involves theremoval of the prostate's core in order to reduce pressure on theurethra. TURP is performed by introducing an electrosurgical cuttingloop through a cystoscope into the urethra and “chipping out” both theprostatic urethra and surrounding prostate tissue up to the surgicalcapsule, thereby completely clearing the obstruction. It will beappreciated that this procedure results in a substantial damageinflicted upon the prostatic urethra.

[0035] With respect to laser ablation of the prostate: laser assistedprostatectomy includes two similar procedures, visual laser ablation ofthe prostate (V-LAP) and contact laser ablation of the prostate (C-LAP),in which a laser fiber catheter is guided through a cystoscope and usedto ablate and coagulate the prostatic urethra and prostatic tissue.Typically, the procedure is performed in the hospital under eithergeneral or spinal anesthesia, and an overnight hospital stay isrequired. In V-LAP, the burnt prostatic tissue then necroses, or diesand over four to twelve weeks is sloughed off during urination. InC-LAP, the prostatic and urethral tissue is burned on contact andvaporized. Again, it will be appreciated that these procedures result ina substantial damage inflicted upon the prostatic urethra.

[0036] With respect to heat ablation therapies: these therapies, underdevelopment or practice, are non-surgical, catheter based therapies thatuse thermal energy to preferentially heat diseased areas of the prostateto a temperature sufficient to cause cell death. Thermal energy formsbeing utilized include microwave, radio frequency (RF) and highfrequency ultrasound energy (HIFU). Both microwave and RF therapysystems are currently being marketed worldwide. Heat ablationtechniques, however, burn the tissue, causing irreversible damage toperipheral tissue due to protein denaturation, and destruction of nervesand blood vessels. Furthermore, heat generation causes secretion ofsubstances from the tissue which may endanger the surrounding area.

[0037] With respect to transurethral RF therapy: transurethral needleablation (TUNA) heats and destroys enlarged prostate tissue by sendingradio waves through needles urethrally positioned in the prostate gland.The procedures prolongs about 35 to 45 minutes and may be performed asan outpatient procedure. However TUNA is less effective than traditionalsurgery in reducing symptoms and improving urine flow. TUNA also burnthe tissue, causing irreversible damage to peripheral tissue due toprotein denaturation, and destruction of nerves and blood vessels.Furthermore, as already discussed above, heat generation causessecretion of substances from the tissue which may endanger thesurrounding area.

[0038] In contrast to the alternative treatments for BPH listed above,cryoablation therapy presents significant advantages. The volume of anenlarged prostate can be reduced, and stricture to the urethra can beeliminated, by selective destruction of prostate tissue by cryoablation.Tissues destroyed by cryoablation in treating BPH are gradually absorbedby the body, rather than being sloughed off during urination.

[0039] When the tissues to be cryoablated are appropriately selected andaccurately cryoablated, there may be minimal endangerment of vitalhealthy functional tissues in proximity to the prostate. Thus,cryoablation is an important technique for treating BPH and haspotential for becoming an increasingly popular therapy and enablingtreatment of a large population of sufferers who today receive noeffective treatment at all for their condition.

[0040] Thus, there is a widely recognized need for, and it would behighly advantageous to have, apparatus and method facilitating theplanning cryoablation for the treatment of BPH by recommendingappropriate number or placement of loci for cryoablation based on apatient's symptomatology, thereby helping to make this useful therapyaccessible to surgeons not specialized in this specific method oftreatment.

[0041] Particularly for surgeons who are not specialists in theparticular limited field of cryoablation of the prostate, there is awidely recognized need for, and it would be highly advantageous to have,apparatus and method which facilitates the execution of a plannedcryoablation treatment of the prostate or of another organ by providingfeedback on the progress of an intervention by comparing real-timeimaging of the intervention site with a planning model of the site,providing warnings when freezing, visible in ultrasound, approachesareas designated as needing to be protected from damage, or whendestruction of tissues risks failing to cover volumes designated asrequiring to be destroyed. Similarly, there is a widely recognized needfor, and it would be highly advantageous to have, mechanisms for guidingmovements of an operator during a cryoablation procedure, or forautomatically managing the movement of cryosurgical tools such ascryoprobes during a cryoablation intervention, according to informationbased on a plan of the intervention and feedback obtained throughreal-time imaging of the intervention site.

[0042] In one respect, a system for planning a cryoablation interventionis particularly useful. Prior art has given little consideration to theinteractive effects of a plurality of closely placed cryoprobes. Yettissues which are in proximity to two or more cryoprobes may be cooledby several sources simultaneously, and consequently achieve a lowertemperature than would be expected when considering the well-knownfreezing patterns created by a single cryoprobe used in isolation.

[0043] Thus there is a widely recognized need for, and it would behighly advantageous to have, system and method for utilizing a pluralityof cryoprobes that takes into account their mutually-reinforcing coolingeffect to create a near-uniform cold field within a volume. It wouldfurther be advantageous to have a system and method for defining avolume in which cognizance is take of the mutually reinforcing coolingeffect of a plurality of closely placed cryoprobes to smoothly andaccurately define a border of a cryoablation volume, thereby ensuringtotal destruction of tissues within that volume while minimizing damageto tissues outside that volume.

SUMMARY OF THE INVENTION

[0044] According to one aspect of the present invention there isprovided a planning system for planning a cryosurgical ablationprocedure, comprising a first imaging modality for creating digitizedpreparatory images of an intervention site, a three-dimensional modelerfor creating a three-dimensional model of the intervention site based onthe digitized preparatory images; and a simulator for simulating acryosurgical intervention, having an interface useable by an operatorfor specifying loci for insertion of cryoprobes and operationalparameters for operation of the cryoprobes for cryoablating tissues, anda displayer for displaying in a common virtual space an integrated imagecomprising a display of said three-dimensional model of saidintervention site and a virtual display of cryoprobes inserted at saidloci.

[0045] According to further features in preferred embodiments of theinvention described below, the planning system further comprises amemory for storing said specified loci for insertion of cryoprobes andsaid operational parameters for operation of said cryoprobes.

[0046] According to still further features in the described preferredembodiments the first imaging modality is selected from the groupconsisting of magnetic resonance imaging, ultrasound imaging andcomputerized tomography imaging, and the three-dimensional model isexpressible in a three-dimensional Cartesion coordinate system.

[0047] According to still further features in the described preferredembodiments the interface also serves for highlighting selected regionswithin the three-dimensional model, and the integrated image furthercomprises a display of an operator-highlighted regions. The interface isuseable by an operator for identifying tissues to be cryoablated and foridentifying tissues to be protected from damage during cryoablation, andthe integrated image further comprises a display of saidoperator-identified tissues to be cryoablated and of saidoperator-identified tissues to be protected from damage during saidcryoablation.

[0048] According to still further features in the described preferredembodiments the system further comprises a predictor for predicting aneffect on tissues of the patient of operation of the cryoprobes at theloci according to the operational parameters, and the model displayeradditionally displays in the common virtual space a representation ofthe predicted effect.

[0049] According to still further features in the described preferredembodiments, the system further comprises an evaluator for comparing thepredicted effect to an operator-defined goal of the procedure. Theevaluator is for identifying areas of predicted less-than-totaldestruction of tissues within a volume of desired total destruction oftissues as defined by an operator, and for identifying areas specifiedas requiring protection during cryoablation which may be endangered by aspecified planned cryoablation procedure.

[0050] According to still further features in the described preferredembodiments, the system comprises a recommender for recommendingcryosurgical procedures to an operator, the recommendation being basedon goals of a cryoablation procedure, the goals being specified by anoperator, and further being based on the three-dimensional model of thesite, thereby facilitating planning the cryoablation procedure. Therecommender may recommend an optimal number of cryoprobes for use in acryoablation procedure, or an optimal temperature for a cryoprobe foruse in a cryoablation procedure, or an optimal duration of cooling for acryoprobe for use in a cryoablation procedure. The recommendation may bebased on a table of optimal interventions based on expertrecommendations, or on a table of optimal interventions based oncompiled feedback from a plurality of operators, and may comprisespecific locations for insertion of a cryoprobe to affect cryoablation.The recommended procedures may be for cryoablation of tissues of aprostate, for treating BPH percutaneously or transperineally, or fortreating a mass or a malignancy. The table may comprise a measure ofvolume of a prostate, or a measure of length of a stricture of a urethraor a measure of symptomatic severity of a BPH condition such as an AUAquestionnaire score.

[0051] The recommendation may be of multiple cryoprobes closely placedso as to ensure a continuous cold field sufficient to ensure completedestruction of tissues within a target volume, while minimizing damageto tissues outside said target volume.

[0052] According to another aspect of the present invention there isprovided a surgical facilitation system for facilitating a cryosurgeryablation procedure, comprising a first imaging modality, for creatingdigitized preparatory images of an intervention site, athree-dimensional modeler for creating a first three-dimensional modelof the intervention site based on the digitized preparatory images, asecond imaging modality, for creating a digitized real-time image of atleast a portion of the intervention site during a cryosurgery procedure,and an images integrator for integrating information from thethree-dimensional model of the site and from the real-time image of thesite in a common coordinate system, thereby producing an integratedimage.

[0053] According to further features in preferred embodiments of theinvention described below, the surgical facilitation system furthercomprising a planning system as described hereinabove.

[0054] According to still further features in the described preferredembodiments the surgical facilitation system further comprises adisplayer for displaying the integrated image in a common virtual space.The displayed integrated image may be a two-dimensional image or athree-dimensional image.

[0055] According to still further features in the described preferredembodiments the surgical facilitation system further comprises athree-dimensional modeler for creating a second three-dimensional modelof at least a portion of the intervention site based on a plurality ofreal-time images. The images integrator may be operable for integratinginformation from the first three-dimensional model of the site and fromthe second three-dimensional model of at least a portion of the site ina common coordinate system.

[0056] According to still further features in the described preferredembodiments the first imaging modality comprises at least one of a groupcomprising magnetic resonance imaging, ultrasound imaging, andcomputerized tomography imaging, and the second imaging modalitycomprises at least one of a group comprising magnetic resonance imaging,ultrasound imaging, and computerized tomography imaging.

[0057] According to still further features in the described preferredembodiments the second imaging modality comprises an imaging tooloperable to report a position of the tool during creation of thereal-time image, thereby providing localizing information about thereal-time image useable by the images integrator.

[0058] According to still further features in the described preferredembodiments the imaging tool is an ultrasound probe inserted in therectum of a patient and operable to report a distance of penetration inthe rectum of the patient during creation of ultrasound images of aprostate of the patient.

[0059] According to still further features in the described preferredembodiments the first three-dimensional model is expressed in athree-dimensional Cartesian coordinate system.

[0060] According to still further features in the described preferredembodiments the surgical facilitation system further comprises aninterface useable by an operator for highlighting selected regionswithin the first three-dimensional model and the integrated imagefurther comprises a display of an operator-highlighted region. Theinterface is useable by an operator for identifying tissues to becryoablated or for identifying tissues to be protected from damageduring cryoablation, and integrated image further comprises a display ofoperator-identified tissues to be cryoablated or of operator-identifiedtissues to be protected from damage during said cryoablation. Theinterface is also useable by an operator for labeling topographicfeatures of the first three-dimensional model and of the real-timeimages or of the second three-dimensional model.

[0061] According to still further features in the described preferredembodiments the images integrator matches operator-labeled topographicfeatures of the first three-dimensional model with operator-labeledfeatures of the real-time images, to orient the first three-dimensionalmodel and the real-time image with respect to the common coordinatesystem.

[0062] According to still further features in the described preferredembodiments the images integrator matches operator-labeled topographicfeatures of the first three-dimensional model with operator-labeledfeatures of the second three-dimensional model, to orient the firstthree-dimensional model and second three-dimensional model with respectto a common coordinate system.

[0063] According to still further features in the described preferredembodiments comprises a simulator for simulating a cryosurgicalintervention, the simulator comprising an interface useable by anoperator during a planning phase of the intervention, for specifyingloci for insertion of cryoprobes and operational parameters foroperation of the cryoprobes for cryoablating tissues, the imageintegrator being operable to integrate the operator-specified loci forinsertion of cryoprobes into the integrated image, and the displayerbeing operable to display the integrated image.

[0064] According to still further features in the described preferredembodiments the surgical facilitation system further comprises a firstcomparator for comparing the first three-dimensional model with thereal-time image to determine differences, a representation of thedifferences being further displayed by the displayer in the integratedimage.

[0065] According to still further features in the described preferredembodiments the surgical facilitation system further comprises apparatusfor providing feedback to an operator regarding position of tools beingused during a surgical intervention as compared to the loci forinsertion of cryoprobes specified by an operator during the planningphase of the intervention. The system further comprises apparatus forproviding feedback to an operator regarding position of tools being usedduring a surgical intervention as compared to operator-identifiedtissues to be cryoablated, and apparatus for providing feedback to anoperator regarding position of tools being used during a surgicalintervention as compared to operator-identified tissues to be protectedduring cryoablation, and apparatus for guiding an operator in theplacement of cryoprobes for affecting cryoablation, the guiding beingaccording to the loci for insertion of cryoprobes specified by anoperating during the planning phase of the intervention.

[0066] According to still further features in the described preferredembodiments the surgical facilitation system further comprises apparatusfor limiting movement of a cryoprobes during a cryoablationintervention, the limitation being according to the loci for insertionof cryoprobes specified by an operating during the planning phase of theintervention.

[0067] According to still further features in the described preferredembodiments the surgical facilitation system further comprises acryoprobe displacement apparatus for moving at least one cryoprobe to atleast one of the loci for insertion of cryoprobes specified by anoperating during the planning phase of the intervention.

[0068] According to still further features in the described preferredembodiments the cryoprobe displacement apparatus comprises a steppermotor and a position sensor, and the surgical facilitation system isoperable to affect cooling of the at least one cryoprobe, heating of atleast one cryoprobe, and is operable to affect scheduled movement of atleast one cryoprobe coordinated with scheduled alternative heating andcooling of at least one cryoprobe, to affect cryoablation at a pluralityof loci.

[0069] According to yet another aspect of the present invention there isprovided a cryoablation method for ensuring complete destruction oftissues within a selected target volume while minimizing destruction oftissues outside the selected target volume, comprising deploying aplurality of cryoprobes in a dense array within the target volume, andcooling the cryoprobes to affect cryoablation, while limiting thecooling to a temperature only slightly below a temperature ensuringcomplete destruction of tissues, thereby limiting destructive range ofeach cooled cryoprobe, the plurality of cryoprobes being deployed in anarray sufficiently dense to ensure destruction of tissues within thetarget volume.

[0070] According to still further features in the described preferredembodiments the method further comprises a planner for planning thedense array, the planner utilizing a three-dimensional model of thetarget volume to calculate a required density of the dense array ofdeployed cryoprobes operated at a selected temperature, to affectcomplete destruction of tissues within the selected target volume.

[0071] According to still further features in the described preferredembodiments the method further comprises using a planner for planningthe dense array, the planner utilizing a three-dimensional model of thetarget volume to calculate, for a plurality of cryoprobes deployed to aselected array of freezing loci, a temperature and duration of coolingfor each of the cryoprobes sufficient to affect complete destruction oftissues within the selected target volume, while also minimizing coolingof tissues outside of the selected target volume.

[0072] According to yet another aspect of the present invention there isprovided a cryoablation method ensuring complete destruction of tissueswithin a selected target volume while minimizing destruction of tissuesoutside the selected target volume, comprising utilizing cryoprobes toaffect cryoablation at a plurality of freezing loci, the loci being of afirst type and of a second type, the first type being located adjacentto a surface of the selected target volume and the second type beinglocated at an interior portion of the selected target volume, andcooling cryoprobes deployed at loci of the first type to a first degreeof cooling and cooling cryoprobes deployed at loci of the second type toa second degree of cooling, the first degree of cooling being lesscooling than the second degree of cooling, thereby affecting wide areasof destruction around each cryoprobe deployed at loci of the second typeand narrow areas of destruction around each cryoprobe deployed at lociof the first type, thereby ensuring complete destruction of tissueswithin a selected target volume while minimizing destruction of tissuesoutside the selected target volume.

[0073] According to still further features in the described preferredembodiments cryoprobes deployed to freezing loci of the first type arecooled to a first temperature and cryoprobes deployed to freezing lociof the second type are cooled to a second temperature, the secondtemperature being lower than the first temperature.

[0074] According to still further features in the described preferredembodiments cryoprobes deployed to freezing loci of the first type arecooled for a first length of time, and cryoprobes deployed to freezingloci of the second type are cooled for a second length of time, thesecond length of time being longer than the first length of time.

[0075] According to still further features in the described preferredembodiments the method further comprises a planner for planning thedense array, the planner utilizing a three-dimensional model of thetarget volume to calculate, for a given array of freezing loci, arequired temperature and length of cooling time for loci of the firsttype and for loci of the second type, to affect complete destruction oftissues within the selected target volume while minimizing destructionof issues outside the selected target volume.

[0076] According to yet another aspect of the present invention there isprovided a method for planning a cryosurgical ablation procedure,comprising utilizing a first imaging modality to create digitizedpreparatory images of an intervention site, utilizing athree-dimensional modeler to create a three-dimensional model of theintervention site based on the digitized preparatory images, andutilizing a simulator having an interface useable by an operator forspecifying loci for insertion of cryoprobes and for specifyingoperational parameters for operation of the cryoprobes, to specify locifor insertion of cryoprobes and operational parameters for operation ofthe cryoprobes for cryoablating tissues, thereby simulating a plannedcryosurgical ablation procedure.

[0077] According to still further features in the described preferredembodiments, the method further comprises utilizing a displayer todisplay in a common virtual space an integrated image comprising adisplay of the three-dimensional model of the intervention site and avirtual display of cryoprobes inserted at the loci, and utilizing amemory to store the specified loci for insertion of cryoprobes and theoperational parameters for operation of the cryoprobes. The firstimaging modality is selected from the group consisting of magneticresonance imaging, ultrasound imaging and computerized tomographyimaging. The three-dimensional model is expressible in athree-dimensional Cartesian coordinate system. The method furthercomprises utilizing the interface to highlight selected regions withinthe three-dimensional model. Highlighting maybe be used to identifytissues to be cryoablated and to identify tissues to be protected fromdamage during cryoablation.

[0078] According to still further features in the described preferredembodiments the method further comprises utilizing a predictor topredict an effect on tissues of the patient of operation of thecryoprobes at the loci according to the operational parameters, and themodel displayer additionally displays in the common virtual space arepresentation of the predicted effect.

[0079] According to still further features in the described preferredembodiments the method further comprises utilizing an evaluator tocompare the predicted effect to an operator-defined goal of theprocedure.

[0080] According to still further features in the described preferredembodiments the method further comprising utilizing the evaluator toidentify areas of predicted less-than-total destruction of tissueswithin a volume of desired total destruction of tissues as defined by anoperator, and utilizing the evaluator to identify areas specified asrequiring protection during cryoablation which may be endangered by aspecified planned cryoablation procedure.

[0081] According to still further features in the described preferredembodiments the method further comprises utilizing a recommender forrecommending cryosurgical procedures, the recommendation being based ongoals of a cryoablation procedure, the goals being specified by anoperator, and further being based on the three-dimensional model of thesite. The recommender recommends an optimal number of cryoprobes for usein a cryoablation procedure, an optimal temperature for a cryoprobe foruse in a cryoablation procedure, an optimal duration of cooling for acryoprobe for use in a cryoablation procedure. The recommendation isbased on a table of optimal interventions based on expertrecommendations, or on a table of optimal interventions based oncompiled feedback from a plurality of operators.

[0082] According to still further features in the described preferredembodiments the recommendation comprises specific locations forinsertion of a cryoprobe to affect cryoablation.

[0083] According to still further features in the described preferredembodiments the recommended procedures are for cryoablation of tissuesof a prostate.

[0084] According to still further features in the described preferredembodiments the recommended procedures are for treating BPH,percutaneously or transperineally.

[0085] According to still further features in the described preferredembodiments the recommended procedures are for treating a mass.

[0086] According to still further features in the described preferredembodiments the recommended procedures are for treating a malignancy.

[0087] According to still further features in the described preferredembodiments the table comprises a measure of volume of a prostate.

[0088] According to still further features in the described preferredembodiments the table comprises a measure of length of a stricture of aurethra.

[0089] According to still further features in the described preferredembodiments the table comprises a measure of symptomatic severity of aBPH condition.

[0090] According to still further features in the described preferredembodiments the measure of symptomatic severity of a BPH condition is anAUA score.

[0091] According to still further features in the described preferredembodiments the recommendation is of multiple cryoprobes closely placedso as to ensure a continuous cold field sufficient to ensure completedestruction of tissues within a target volume, while minimizing damageto tissues outside the target volume.

[0092] According to still another aspect of the present invention thereis provided a method for facilitating a cryosurgery ablation procedure,comprising utilizing a first imaging modality for creating digitizedpreparatory images of an intervention site, utilizing athree-dimensional modeler for creating a first three-dimensional modelof the intervention site based on the digitized preparatory images,utilizing a second imaging modality for creating a digitized real-timeimage of at least a portion of the intervention site during acryosurgery procedure, and utilizing an images integrator forintegrating information from the three-dimensional model of the site andfrom the real-time image of the site in a common coordinate system,thereby producing an integrated image the site, facilitative to anoperator practicing a cryoablation procedure.

[0093] According to still further features in the described preferredembodiments the method further comprises utilizing a planning method.

[0094] According to still further features in the described preferredembodiments the method further comprises utilizing a displayer fordisplaying the integrated image in a common virtual space.

[0095] According to still further features in the described preferredembodiments the displayed integrated image is a two-dimensional image.

[0096] According to still further features in the described preferredembodiments the displayed integrated image is a three-dimensional image.

[0097] According to still further features in the described preferredembodiments the method further comprises utilizing a three-dimensionalmodeler for creating a second three-dimensional model of at least aportion of the intervention site based on a plurality of real-timeimages.

[0098] According to still further features in the described preferredembodiments he method further comprises utilizing the images integratorto integrate information from the first three-dimensional model of thesite and from the second three-dimensional model of at least a portionof the site in a common coordinate system.

[0099] According to still further features in the described preferredembodiments the first imaging modality comprises at least one of a groupcomprising magnetic resonance imaging, ultrasound imaging, andcomputerized tomography imaging.

[0100] According to still further features in the described preferredembodiments the second imaging modality comprises at least one of agroup comprising magnetic resonance imaging, ultrasound imaging, andcomputerized tomography imaging.

[0101] According to still further features in the described preferredembodiments the method further comprises utilizing an imaging tool toreport a position of the tool during creation of the real-time image,thereby providing localizing information about the real-time imageuseable by the images integrator.

[0102] According to still further features in the described preferredembodiments the imaging tool is an ultrasound probe inserted in therectum of a patient operated to report a distance of penetration of thetool in the rectum of the patient during creation of ultrasound imagesof a prostate of the patient.

[0103] According to still further features in the described preferredembodiments the first three-dimensional model is expressed in athree-dimensional Cartesian coordinate system.

[0104] According to still further features in the described preferredembodiments the method further comprises utilizing an interface tohighlight selected regions within the first three-dimensional model.

[0105] According to still further features in the described preferredembodiments the integrated image comprises a display of anoperator-highlighted region.

[0106] According to still further features in the described preferredembodiments the method further comprises utilizing the interface foridentifying tissues to be cryoablated.

[0107] According to still further features in the described preferredembodiments the integrated image further comprises a display of theoperator-identified tissues to be cryoablated.

[0108] According to still further features in the described preferredembodiments he method further comprises utilizing the interface foridentifying tissues to be protected from damage during cryoablation.

[0109] According to still further features in the described preferredembodiments the integrated image further comprises a display of theoperator-identified tissues to be protected from damage during thecryoablation.

[0110] According to still further features in the described preferredembodiments the method further comprises utilizing the interface forlabeling topographic features of the first three-dimensional model.

[0111] According to still further features in the described preferredembodiments the method further comprises utilizing the interface forlabeling topographic features of the real-time images.

[0112] According to still further features in the described preferredembodiments the method further comprises utilizing the interface forlabeling topographic features of the second three-dimensional model.

[0113] According to still further features in the described preferredembodiments the images integrator matches operator-labeled topographicfeatures of the first three-dimensional model with operator-labeledfeatures of the real-time images, to orient the first three-dimensionalmodel and the real-time image with respect to the common coordinatesystem.

[0114] According to still further features in the described preferredembodiments the images integrator matches operator-labeled topographicfeatures of the first three-dimensional model with operator-labeledfeatures of the second three-dimensional model, to orient the firstthree-dimensional model and second three-dimensional model with respectto the common coordinate system.

[0115] According to still further features in the described preferredembodiments the method further comprises simulating a cryosurgicalintervention by utilizing a simulator having an interface, and utilizingthe interface during a planning phase of the intervention to specifyloci for insertion of cryoprobes into a cryoablation site in a patientand to specify operational parameters for operation of the cryoprobesfor cryoablating tissues, and further utilizing the image integrator tointegrate the specified loci into the integrated image, and utilizingthe displayer to display the integrated image.

[0116] According to still further features in the described preferredembodiments the method further comprises simulating a cryosurgicalintervention by receiving from an operator during a planning phase ofthe intervention specifications of loci for insertion of cryoprobes intoa cryoablation site and operational parameters for operation of thecryoprobes for cryoablating tissues, utilizing the image integrator tointegrate the operator-specified loci into the integrated image, andutilizing the displayer to display the integrated image.

[0117] According to still further features in the described preferredembodiments the method further comprises utilizing a first comparatorfor comparing the first three-dimensional model with the real-time imageto determine differences.

[0118] According to still further features in the described preferredembodiments the method further comprises utilizing apparatus forproviding feedback to an operator regarding position of tools being usedduring a surgical intervention as compared to the loci for insertion ofcryoprobes specified by an operator during the planning phase of theintervention.

[0119] According to still further features in the described preferredembodiments the method further comprises providing feedback to anoperator regarding a position of a tool being used during a surgicalintervention as compared to the loci for insertion of cryoprobesspecified by an operator during the planning phase of the intervention.

[0120] According to still further features in the described preferredembodiments the method further comprises utilizing apparatus forproviding feedback to an operator regarding a position of a tool beingused during a surgical intervention as compared to a position ofoperator-identified tissues to be cryoablated.

[0121] According to still further features in the described preferredembodiments the method further comprises utilizing apparatus forproviding feedback to an operator regarding a position of a tool beingused during a surgical intervention as compared to a position ofoperator-identified tissues to be protected during cryoablation.

[0122] According to still further features in the described preferredembodiments the method further comprises utilizing apparatus for guidingan operator in the placement of cryoprobes for affecting cryoablation,the guiding being according to the loci for insertion of cryoprobesspecified by an operating during the planning phase of the intervention.

[0123] According to still further features in the described preferredembodiments the method further comprises guiding an operator in theplacement of cryoprobes for affecting cryoablation, the guiding beingaccording to the loci for insertion of cryoprobes specified by anoperating during the planning phase of the intervention.

[0124] According to still further features in the described preferredembodiments the method further comprises utilizing apparatus forlimiting movement of a cryoprobe during a cryoablation intervention, thelimitation being according to the loci for insertion of cryoprobesspecified by an operating during the planning phase of the intervention.

[0125] According to still further features in the described preferredembodiments the method further comprises utilizing cryoprobedisplacement apparatus for moving at least one cryoprobe to at least oneof the loci for insertion of cryoprobes specified by an operator duringthe planning phase of the intervention.

[0126] According to still further features in the described preferredembodiments the method further comprises utilizing a stepper motor tomove the cryoprobe.

[0127] According to still further features in the described preferredembodiments the method further comprises utilizing a position sensor tosense a position of the cryoprobe.

[0128] According to still further features in the described preferredembodiments the method further comprises utilizing control apparatus tocontrol cooling of the at least one cryoprobe.

[0129] According to still further features in the described preferredembodiments the method further comprises utilizing control apparatus tocontrol heating of the at least one cryoprobe.

[0130] According to still further features in the described preferredembodiments the method further comprises controlling the at least onecryoprobe according to a schedule of movements coordinated with aschedule of alternative heating and cooling of the at least onecryoprobe, to affect cryoablation at a plurality of loci.

[0131] The present invention successfully addresses the shortcomings ofthe presently known configurations by providing a system and method foreffectively planning a cryoablation procedure by simulating such aprocedure based on preparatory imaging of a target site in a patient, bysimulating the procedure, by recommending procedural steps and byevaluating procedural steps specified by a user.

[0132] The present invention further successfully addresses theshortcomings of the presently known configurations by providing a systemand method for facilitating a cryoablation intervention by relatingpreparatory imaging of a site, and plans for intervening at that site,to real-time images of the site during cryoablation.

[0133] The present invention further successfully addresses theshortcomings of the presently known configurations by providing a systemand method for completely destroying target tissues at a cryoablationsite while limiting damage to healthy tissues in close proximity to thatsite.

[0134] Implementation of the method and the apparatus of the presentinvention involves performing or completing selected tasks or stepsmanually, automatically, or a combination thereof. Moreover, accordingto actual instrumentation and equipment of preferred embodiments of themethod and apparatus of the present invention, several selected stepscould be implemented by hardware or by software on any operating systemof any firmware or a combination thereof. For example, as hardware,control of selected steps of the invention could be implemented as achip or a circuit. As software, control of selected steps of theinvention could be implemented as a plurality of software instructionsbeing executed by a computer using any suitable operating system. In anycase, selected steps of the method of the invention could be describedas being controlled by a data processor, such as a computing platformfor executing a plurality of instructions.

BRIEF DESCRIPTION OF THE DRAWINGS

[0135] The invention is herein described, by way of example only, withreference to the accompanying drawings. With specific reference now tothe drawings in detail, it is stressed that the particulars shown are byway of example and for purposes of illustrative discussion of thepreferred embodiments of the present invention only, and are presentedin the cause of providing what is believed to be the most useful andreadily understood description of the principles and conceptual aspectsof the invention. In this regard, no attempt is made to show structuraldetails of the invention in more detail than is necessary for afundamental understanding of the invention, the description taken withthe drawings making apparent to those skilled in the art how the severalforms of the invention may be embodied in practice.

[0136] In the drawings:

[0137]FIG. 1a is a graph showing the profile of temperature distributionwithin an ice-ball formed at the tip of a cryosurgical probe;

[0138]FIG. 1b is a graph showing the effectiveness of a cryosurgicaltreatment, given in percentage of tissue destruction, as a function oftemperature;

[0139]FIGS. 2a-2 c are cross sectional views of an ice-ball formed atthe tip of a conventional cryosurgical probe introduced into a patient'sprostate;

[0140]FIGS. 3a-3 b are cross sectional views of two ice-balls formed atthe tips of cryosurgical probes introduced into a patient's prostate,according to methods of the prior art;

[0141]FIG. 4 is a cross sectional view illustrating a method fortreating a patient's prostate, according to methods of the prior art;

[0142]FIG. 5 is a cross sectional view illustrating a further method fortreating a patient's prostate, according to methods of the prior art;

[0143]FIG. 6a is a schematic illustration of a multi-probe cryosurgicaldevice according to methods of the prior art;

[0144]FIG. 6b is a schematic illustration of a pre-cooling elementaccording to methods of the prior art;

[0145]FIG. 7 is a schematic longitudinal section of a preferredcryosurgical probe according to methods of the prior art;

[0146]FIG. 8 is a perspective view of a guiding element for receivingcryosurgical probes, the guiding element being connected to anultrasound probe, according to methods of the prior art;

[0147]FIGS. 9 and 10 illustrate a method including the steps of forminga three-dimensional grid of a patient's prostate and introducingcryosurgical probes thereto, according to methods of the prior art;

[0148]FIG. 11 is a simplified block diagram of a planning system forplanning a cryoablation procedure, according to a first preferredembodiment of the present invention;

[0149]FIGS. 12a-12 b are a flow chart showing a method for automaticallygenerating a recommendation relating to a cryoablation procedure,according to an embodiment of the present invention;

[0150]FIG. 13 is a chart showing temperature profiles for severalcryoablation methods, is useful for understanding FIGS. 14 and 15;

[0151]FIG. 14 is a simplified flow chart showing a method for ensuringtotal destruction of a selected volume while limiting damage to tissuesoutside that selected volume, according to an embodiment of the presentinvention;

[0152]FIG. 15 is a simplified flow chart showing another method forensuring total destruction of a selected volume while limiting damage totissues outside that selected volume, according to an embodiment of thepresent invention;

[0153]FIG. 16 is a simplified block diagram of surgical facilitationsystem for facilitating a cryosurgery ablation procedure, according toan embodiment of the present invention; and

[0154]FIG. 17 is a schematic diagram of mechanisms for control ofcryosurgical tools by a surgical facilitation system, according to anembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0155] The present invention relates to system and method for planning acryoablation procedure and to system and method for facilitating acryoablation procedure. More particularly, the present invention relatesto the use of integrated images displaying, in a common virtual space, athree-dimensional model of a surgical intervention site based ondigitized preparatory images of the site from first imaging modalities,simulation images of cryoprobes used according to an operator-plannedcryoablation procedure at the site, and real-time images provided bysecond imaging modalities during cryoablation. The present inventionfurther relates to system-supplied recommendations for and evaluationsof the planned cryoablation procedure, and to system-supplied feedbackto an operator and system-supplied guidance and control signals foroperating a cryosurgery tool during cryoablation. The present inventionstill further relates to methods for generating a nearly-uniform coldfield among a plurality of cryoprobes, for cryoablating a volume withsmooth and well-defined borders.

[0156] For purposes of better understanding the present invention,reference is first made to the construction and operation ofconventional (i.e., prior art) systems as illustrated in FIGS. 1-10.

[0157]FIG. 1a illustrates the profile of temperature distribution acrossan ice-ball formed at the tip of a cryosurgical probe. As shown, thetemperature at a surface 5 of the ice ball is 0° C. The temperaturedeclines exponentially towards a center 1 of the ball where itpreferably reaches the value of −170° C., such that an isothermalsurface 7 of about −40° C. is typically located within the ice-ball atthe half way between the center of the ball and its surface. Thus, ifthe ice ball features a radius R, then the radius of the −40° c.isothermal surface 7 is about R/2.

[0158]FIG. 1b is a graph showing the effectiveness of a cryosurgicaltreatment (given in percentage of tissue destruction) as a function oftemperature. As shown, the temperature required for effectivelydestroying a tissue is at least about −40° C. Accordingly, in order toeffectively destroy a tissue, the isothermal surface of −40° C. (shownin FIG. 1a) should be placed at the periphery of the treated tissue sothat the entire area of the treated tissue is exposed to at least about−40° C., thereby exposing adjacent health tissues and organs to theexternal portion of the ice-ball. The application of temperatures ofbetween about −40° C. and 0° C. to such healthy tissues usually causessubstantial damage thereto, which damage may result in temporary orpermanent impairment of functional organs.

[0159]FIGS. 2a-2 c illustrate prior-art cryosurgical methods wherein asingle cryosurgical probe of a substantially large diameter, typically3-5 millimeters, is introduced between the patient's prostatic urethraand the periphery of the prostate, so as to destroy the prostatic tissueextending therebetween.

[0160] Specifically, FIGS. 2a-2 c are cross sectional views of anice-ball 9 formed at the end of a conventional cryosurgical tipintroduced into a prostate 2 of a patient. The patient's prostaticurethra, rectum and nerves are designated as 4, 3, and 6 respectively.

[0161] A single ice-ball 9 is formed within the prostatic tissue segmentextending between the prostatic urethra 4 and the periphery of theprostate 13. The dimensions of a conventional cryosurgical probe aredesigned so as to provide an ice-ball 9 having an inner portion 10extending through a substantially significant portion of such a tissuesegment, so as to apply temperatures of between about −170° C. and about−40° C. thereto. The application of a single probe for producing asingle ice-ball 9 imposes a trade-off between several options.

[0162]FIGS. 2a and 2 b illustrate the trade-off between a first optionof avoiding the damaging of the patient's prostatic urethra 4 yetdamaging nerves 6 present close to the periphery 13 of the prostate 2(FIG. 2a), and a second option of avoiding the damaging of the patient'snerves 6 yet damaging urethra 4 (FIG. 2b).

[0163] As shown in FIG. 2a, the isothermal surface 7 of −40° C. ispositioned substantially at the periphery 13 of the patient's prostate2, such that surface 5 of the ice-ball 9 is positioned substantiallynear the patient's urethra 4, so as to avoid damaging of the patient'surethra 4. Thus, the inner portion 10 of ice-ball 9 effectively freezesthe peripheral regions (in cross section) of the prostate, while outerportion 12 of ice-ball 9 extends through the patient's nerves 6. Theapplication of temperatures of between about −40° C. and 0° C. to thepatient's nerves 6 may result in temporary or permanent impairmentthereof.

[0164] Similarly, when ice-ball 9 is positioned between the patient'surethra 4 and rectum 3 in such a manner so as to avoid the damaging ofurethra 4, the application of between about −40° C. and 0° C. to thepatient's rectum may result in temporary or permanent impairmentthereof.

[0165] As shown in FIG. 2b, the isothermal surface 7 of −40° C. ispositioned substantially near the patient's urethra 4 such that surface5 of ice-ball 9 is positioned substantially near the patient's nerves 6and/or rectum 3 (not shown), so as to avoid damaging of the patient'snerves 6 and/or rectum 3. Thus, inner portion 10 of ice-ball 9effectively freezes the central regions (in cross section) of prostate2, while outer portion 12 of ice-ball 9 extends through the patient'surethra 4. The application of temperatures of between about −40° C. and0° C. to the patient's urethra 4 may result in temporary or permanentimpairment thereof.

[0166] However, none of the alternatives shown in FIGS. 2a and 2 bprovides an effective treatment (temperature of at least about −40° C.)to the entire prostatic tissue segment extending between urethra 4 andthe periphery 13 of the prostate, thereby exposing the patient to therisk of malignancy.

[0167]FIG. 2c shows another possible alternative wherein a thickercryosurgical probe, having a tip diameter of between 4 and 6 millimetersis used for producing a lager ice-ball, of about 4-5 centimeters indiameter, so as to enable effective treatment of the entire prostatictissue segment extending between the urethra 4 and periphery 13 ofprostate 2. As shown, inner portion 10 of the ice-ball 9 extends throughthe entire tissue segment (in cross section) between urethra 4 andperiphery 13 of the prostate, thereby exposing urethra 4 and nerves (notshown), as well as the rectum 3, to outer portion 12 of the ice-ball 9.

[0168] The thickness (in cross section) of tissues exposed to outerportion 12 of the ice-ball is about R/2, where R is the radius ofice-ball 9. Thus, the volume of adjacent tissues exposed to damagebecomes substantially greater than the volume of the treated tissue.

[0169] Thus, the conventional cryosurgical probes and methods fail toprovide the necessary resolution of treatment required for enabling anaccurate and effective destruction of a tissue while preserving othertissues and organs adjacent thereto.

[0170]FIGS. 3a and 3 b are schematic illustrations of a cryosurgicalmethod according to another method of prior art, wherein a plurality ofcryosurgical probes of substantially small diameters are introducedbetween the patient's prostatic urethra 4 and periphery 13 of prostate2, so as to destroy the prostatic tissue extending therebetween.

[0171] As shown in FIG. 3a, preferably two probes are introduced into aprostatic tissue segment extending between the patient's prostaticurethra 4 and periphery 13 of prostate 2, so as to form two smallerice-balls, 9 a and 9 b.

[0172] According to the configuration shown in FIG. 3a, each ofice-balls 9 a and 9 b features a radius of R/2, which is half the radiusof ice-ball 9 shown in FIG. 2c. Accordingly, ice-balls 9 a and 9 binclude respective inner portions, 14 a and 14 b, each having a radiusof R/4, and respective outer portions, 16 a and 16 b, each having athickness of R/4.

[0173] Therefore, by introducing two probes of a small diameters ratherthan a single probe of a larger diameter into the tissue segmentextending between prostatic urethra 4 and periphery 13 of prostate 2,the thickness of adjacent tissues exposed to damage is substantiallydecreased. The specific example of FIG. 3a shows that the thickness (incross section) of adjacent tissues exposed to between about −40° C. and0° C. is only R/4, which is half the thickness and respectively muchless the volume (e.g., 8 fold less), exposed to damage when using theprior art method (shown in FIG. 2c).

[0174] By further decreasing the diameter of the cryosurgical probes andintroducing a plurality of probes into the tissue segment extendingbetween urethra 4 and periphery 13 of prostate 2, the damage tosurrounding tissues may be further minimized, thereby improving theresolution of the cryosurgical treatment.

[0175] Another prior art embodiment is shown in FIG. 3b, wherein twoprobes are introduced into the tissue segment extending between thepatient's urethra 4 and periphery 13 of prostate 2, so as to form twoice-balls 9 a and 9 b, such that inner portion 14 a of ice-ball 9 a issubstantially spaced from inner portion 14 b of ice-ball 9 b, and outerportion 16 a of ice-ball 9 a partially overlaps outer portion 16 b ofice-ball 9 b, the overlapping region being designated as 17. Thespecific example shown in FIG. 3b is of two ice-balls each having aradius of R/5, wherein R is the radius of a conventional ice-ball asshown in FIG. 2c. By using such configuration, the thickness of adjacenttissues exposed to damage is decreased to R/5 and the volume thereof isdecreased respectively. It will be appreciated that in the example givensubstantial fractions of region 17, from which heat is extracted by twoprobes, will become cooler than −40° C.

[0176] The specific examples shown in FIGS. 3a and 3 b are of twoice-balls having tangent and spaced inner portions, respectively.However, a plurality of probes may be used, each having a distinctdiameter, the inner portions of which being tangent or spaced.

[0177] Referring to FIG. 4, a prior-art cryosurgical method is shown,illustrating the distribution of a plurality of cryosurgical probesacross a patient's prostate, wherein a single probe is introduce into atissue segment extending between prostatic urethra 4 and periphery 13 ofprostate 2. According to such a prior art method, about 5-7 probes areintroduced into the patient's prostate, wherein each of the probesfeatures a diameter of about 3 millimeters. FIG. 4 shows a specificexample wherein five probes are introduced so as to form five ice-ballshaving inner portions 10 a-10 e and outer portions 12 a-12 e. As shown,an effective treatment is provided by inner portions 10 a-10 e, andregions therebetween marked 19, only to limited regions of the prostate,wherein the damage caused to adjacent tissues such as the patient'surethra 4, rectum 3 and nerve 6 b by outer portions 12 a-12 e isconsiderable.

[0178]FIG. 5 shows a preferred distribution of cryosurgical probesaccording to another method of prior art. As shown, at least twocryosurgical probes of substantially small diameter are introduced intospecific segments of prostatic tissue extending between urethra 4 andperiphery 13 of prostate 2. FIG. 5 shows a specific example whereintwenty probes are introduced into the patient's prostate 2, includingfive pairs of inner and outer cryosurgical probes located at specificsegments of the prostate extending from the urethra 4 to periphery 13,and additional (five pairs in the example given) of outer cryosurgicalprobes are introduced therebetween. The inner portions of the ice-ballsformed by the pairs of outer and inner probes are designated as 14 a and14 b, respectively, wherein the inner portions of the ice-balls formedtherebetween are designated as 14 c.

[0179] The diameter of a single cryosurgical probe according to theprior art method presented in FIG. 5 is preferably between about 1.2millimeters and about 1.4 millimeters.

[0180] As shown, such distribution of substantially small diametercryosurgical probes enables to provide an effective treatment of atleast −40° C. to a larger area of the prostatic tissue whilesubstantially minimizing the thickness of healthy adjacent tissuesexposed to damage.

[0181] Thus, the prior art method presented in FIG. 5 substantiallyincreases the effectiveness and resolution of treatment relative to theprior art method presented by FIG. 4.

[0182] The pattern of distribution of probes shown in FIG. 5 includes aninner circle and an outer circle of probes, wherein a portion of theprobes is arranged in pairs of an inner probe and an outer probe.According to another configuration (not shown), the probes are arrangedin an inner circle and an outer circle, but not necessarily in pairs ofan inner probe and an outer probe.

[0183] The probes may be sequentially introduced to and extracted fromthe patient's prostate so as to sequentially freeze selected portionsthereof. A method of quick extraction of the probes without tearingpieces of tissue from the patient, which stick to the tip of the probe,is disclosed hereinunder.

[0184] The introduction of a plurality of small diameter cryosurgicalprobes improves the resolution of treatment along the planesperpendicular to the axis of penetration of the probes into theprostate. However, the prostate, as other anatomical organs, features anasymmetric three dimensional shape. Thus, a specific pattern ofdistribution of probes may provide an effective treatment to a distinctplane located at a specific depth of penetration, but at the same timemay severely damage non-prostatic tissues located at other depths ofpenetration. There is need for cryosurgical method and apparatus whichenable high resolution of treatment along and perpendicular to the axisof penetration of the probes into a patient's organ. Presentedhereinbelow is a cryosurgical method and apparatus according to priorart which enable high resolution of treatment along the axis ofpenetration of the cryosurgical probe into the patient's organ as wellas along the planes perpendicular to the axis of penetration, whereinthese high resolutions are achieved by forming a three-dimensional gridof the organ, preferably by using ultrasound imaging, and inserting eachof the cryosurgical probes to a specific depth within the organaccording to the information provided by the grid.

[0185] Referring to FIGS. 6a, 6 b and 7, a cryosurgical apparatusaccording to methods of prior art includes a plurality of cryosurgicalprobes 53, each having an operating tip 52 including a Joule-Thomsoncooler for freezing a patient's tissue and a holding member 50 forholding by a surgeon. As shown in FIG. 7, operating tip 52 includes atleast one passageway 78 extending therethrough for providing gas of highpressure to orifice 80 located at the end of operating tip 52, orifice80 being for passage of high pressure gas therethrough, so as to cooloperating tip 52 and produce an ice-ball at its end 90. Gases which maybe used for cooling include, but are not limited to argon, nitrogen,air, krypton, CO₂, CF₄, xenon, or N₂O.

[0186] When a high pressure gas such as argon expands through orifice 80it liquefies, so as to form a cryogenic pool within chamber 82 ofoperating tip 52, which cryogenic pool effectively cools surface 84 ofoperating tip 52. Surface 84 of operating tip 52 is preferably made of aheat conducting material such as metal so as to enable the formation ofan ice-ball at end 90 thereof.

[0187] Alternatively, a high pressure gas such as helium may be used forheating operating tip 52 via a reverse Joule-Thomson process, so as toenable treatment by cycles of cooling-heating, and further forpreventing sticking of the probe to the tissue when extracted from thepatient's body, and to enable fast extraction when so desired.

[0188] When a high pressure gas such as helium expands through orifice80 it heats chamber 82, thereby heating surface 84 of operating tip 52.

[0189] Operating tip 52 includes at least one evacuating passageway 96extending therethrough for evacuating gas from operating tip 52 to theatmosphere.

[0190] As shown FIG. 7, holding member 72 may include a heat exchangerfor pre-cooling the gas flowing through passageway 78. Specifically, theupper portion of passageway 78 may be in the form of a spiral tube 76wrapped around evacuating passageway 96, the spiral tube beingaccommodated within a chamber 98. Thus, gas evacuated through passageway96 may pre-cool the incoming gas flowing through spiral tube 76.

[0191] As further shown in FIG. 7, holding member 72 may include aninsulating body 92 for thermally insulating the heat exchanger from theexternal environment.

[0192] Furthermore, operating tip 52 may include at least one thermalsensor 87 for sensing the temperature within chamber 82, the wire 89 ofwhich extending through evacuating passageway 96 or a dedicatedpassageway (not shown).

[0193] In addition, holding member 72 may include a plurality ofswitches 99 for manually controlling the operation of probe 53 by asurgeon. Such switches may provide functions such as on/off, heating,cooling, and predetermined cycles of heating and cooling by selectivelyand controllably communicating incoming passageway 70 with anappropriate external gas container including a cooling or a heating gas.

[0194] As shown in FIG. 6a, each of cryosurgical probes 53 is connectedvia a flexible connecting line 54 to a connecting site 56 on a housingelement 58, preferably by means of a linking element 51. Cryosurgicalprobes 53 may be detachably connected to connecting sites 56.

[0195] Preferably, evacuating passageway 96 extends through connectingline 54, such that the outgoing gas is evacuated through an openinglocated at linking element 51 or at any other suitable location, e.g.,manifold 55, see below. Preferably, line 54 further includes electricalwires for providing electrical signals to the thermal sensor andswitches (not shown).

[0196] Each of cryosurgical probes 53 is in fluid communication with amanifold 55 received within a housing 58, mainfold 55 being fordistributing the incoming high pressure gas via lines 57 to cryosurgicalprobes 53.

[0197] As shown, housing 58 is connected to a connector 62 via aflexible cable 60 including a gas tube (not shown), connector 62 beingfor connecting the apparatus to a high pressure gas source and anelectrical source.

[0198] The apparatus further includes electrical wires (not shown)extending through cable 60 and housing 58 for providing electricalcommunication between the electrical source and cryosurgical probes 53.

[0199] Preferably, housing 58 includes a pre-cooling element, generallydesignated as 61, for pre-cooing the high pressure gas flowing tocryosurgical probes 53. Preferably, pre-cooling element 61 is aJoule-Thomson cooler, including a tubular member 48 received within achamber 49, tubular member 48 including an orifice 59 for passage ofhigh pressure gas therethrough, so as to cool chamber 49, therebycooling the gas flowing through tubular member 48 into mainfold 55.

[0200] Another configuration of a pre-cooling element 61 is shown inFIG. 6b, wherein tubular member 48 is in the form of a spiral tubewrapped around a cylindrical element 47, so as to increase the area ofcontact between tubular member 48 and the cooling gas in chamber 49.

[0201] According to yet another configuration (not shown), housing 58includes a first tubular member for supplying a first high pressure gasto manifold 55, and a second tubular member for supplying a second highpressure gas to pre-cooling element 61. Any combination of gases may beused for cooling and/or heating the gases flowing through such tubularmembers.

[0202] Alternatively, a cryogenic fluid such as liquid nitrogen may beused for pre-cooling the gas flowing through housing 58. Alternatively,an electrical pre-cooling element may used for pre-cooling the gas.

[0203] Preferably, thermal sensors (not shown) may be located withincable 60 and manifold 55 for measuring the temperature of gas flowingtherethrough.

[0204] Referring to FIGS. 8-10, method and apparatus according to priorart applies an imaging device such as ultrasound, MRI or CT, so as toform a three-dimensional grid of the patient's treated organ, e.g.,prostate, the three dimensional grid serves for providing information onthe three dimensional shape of the organ. Each of the cryosurgicalprobes is then inserted to a specific depth within the organ accordingto the information provided by the grid.

[0205] As shown in FIG. 8, an ultrasound probe 130 is provided forinsertion into the patient's rectum, ultrasound probe 130 being receivedwithin a housing element 128. A guiding element 115 is connected tohousing element 128 by means of a connecting arm 126. As shown, guidingelement 115 is in the form of a plate 110 having a net of apertures 120,each aperture serves for insertion of a cryosurgical probe therethrough.Preferably, the distance between each pair of adjacent apertures 120 isbetween about 2 millimeters and about 5 millimeters.

[0206] As shown in FIG. 9, ultrasound probe 130 is introduced to aspecific depth 113 within the patient's rectum 3. A net of marks 112 isprovided on the obtained ultrasound image 114, the net of marks 112 onimage 114 being accurately correlated to the net of apertures 120 onguiding element 115.

[0207] Thus, marks 112 on image 114 sign the exact locations of thecenters of ice-balls which may be formed at the end of the cryosurgicalprobes inserted through apertures 120 to the patient's prostate 2,wherein image 114 relates to a specific depth of penetration 113 of thecryosurgical probes into the prostate 2.

[0208] As shown in FIG. 9, ultrasound probe 130 is gradually introducedto various depths 113 of rectum 3, thereby producing a set of images114, wherein each image relates to a respective depth of penetrationinto the prostate 2. Thus, each of images 114 relates to a specificplane perpendicular to the axis of penetration of the cryosurgicalprobes.

[0209] The set of images 114 provides a three dimensional grid of theprostate. Such three-dimensional grid is then used for planning thecryosurgical procedure.

[0210] For example, the introduction of a cryosurgical probe along agiven axis of penetration to a first depth may effectively destroy aprostatic tissue segment, while introduction of the probe to a seconddepth may severely damage the prostatic urethra.

[0211] Since the ice-ball is locally formed at the end of thecryosurgical probe, each probe may be introduced to a specific depth soas to locally provide an effective treatment to a limited portion of theprostate while avoiding the damaging of non-prostatic or prostatictissues located at other depths of penetration.

[0212]FIG. 10 shows the insertion of an operating tip 52 of acryosurgical probe 50 through an aperture of guiding element 115 intothe prostate 2 of a patient.

[0213] Preferably, a plurality of cryosurgical probes are sequentiallyinserted through apertures 120 of guiding element 115 into the patient'sprostate, wherein each probe is introduced to a specific depth, therebyproviding substantially local effective treatment to distinct segmentsof the prostatic tissue while avoiding the damaging of other prostaticor nonprostatic tissue segments.

[0214] Preferably, each of the cryosurgical probes includes a scale forindicating the depth of penetration into the prostate.

[0215] Reference is now made to FIG. 11, which is a simplified blockdiagram of a planning system for planning a cryoablation procedure,according to a first preferred embodiment of the present invention.

[0216] In FIG. 11, a planning system 240 for planning a cryoablationprocedure comprises a first imaging modality 250 which serves forcreating digitized preparatory images 254 of a cryoablation interventionsite. First imaging modality 250 will typically be a magnetic resonanceimaging system (MRI), an ultrasound imaging system, a computerizedtomography imaging system (CT), a combination of these systems, or asimilar system able to produce images of the internal tissues andstructures of the body of a patient. First imaging modality 250 is forproducing digitized images of a cryoablation intervention site, whichsite includes body tissues whose cryoablation is desired (referred toherein as “target” tissue), which may be a tumor or other structure, andbody tissues and structures in the immediate neighborhood of the targettissues, which constitute the target tissue's physical environment.

[0217] Some types of equipment useable as first imaging modality 250, aCT system for example, typically produce a digitized image in acomputer-readable format. If equipment used as first imaging modality250 does not intrinsically produce digitized output, as might be thecase for conventional x-ray imaging, then an optional digitizer 252 maybe used to digitize non-digital images, to produce digitized preparatoryimages 254 of the site.

[0218] Digitized images 254 produced by first imaging modality 250 andoptional digitizer 252 are passed to a three-dimensional modeler 256 forcreating a three-dimensional model 258 of the intervention site.Techniques for creating a three dimensional model based on a set of twodimensional images are well known in the art. In the case of CT imaging,creation of a three dimensional model is typically in intrinsic part ofthe imaging process. PROVISION, from Algotec Inc.(http://www.algotec.com/products/provision.htm) is an example ofsoftware designed to make a 2-D to 3-D conversion for images generatedby CT scans. To accomplish the same purpose starting from ultrasoundimaging, SONOReal™ software from BIOMEDICOM (http://www.biomedicom.com/)may be used.

[0219] Three dimensional model 258 is preferably expressible in a threedimensional Cartesian coordinate system.

[0220] Three dimensional model 258 is useable by a similator 260 forsimulating a cryosurgical intervention. Simulator 260 comprises adisplayer 262 for displaying views of model 258, and an an interface 264useable by an operator for specifying loci for insertion of simulatedcryoprobes 266 and operational parameters for operation of simulatedcryoprobes 266 for cryoablating tissues. Thus, an operator (i.e., auser) can use simulator 260 to simulate a cryoablation intervention, byusing interface 264 to command particular views of model 258, and byspecifying both where to insert simulated cryoprobes 266 into an organimaged by model 258, and how to operate cryoprobes 266. Typically, anoperator may specify positions for a plurality of simulated cryoprobes266, and further specify operating temperatures and durations of coolingfor cryoprobes 266. Display 262 is then useable for displaying in acommon virtual space an integrated image 268 comprising a display ofthree dimensional model 258 and a virtual display of simulatedcryoprobes 266 inserted at said operator-specified loci.

[0221] Planning system 240 optionally comprises a memory 270, such as acomputer disk, for storing operator-specified loci for insertion ofcryoprobes and operator-specified parameters for operation simulatedcryoprobes 266.

[0222] Interface 264 comprises a highlighter 280 for highlighting, undercontrol of an operator, selected regions within three dimensional model258. Operator-highlighted selected regions of model 258 are thenoptionally displayed as part of an integrated image 268.

[0223] In particular, highlighter 280 is useable by an operator foridentifying tissues to be cryoablated. Preferably, interface 264 permitsan operator to highlight selected regions of three dimensional model 258so as to specify therein tissues to be cryoablated, or alternativelyinterface 264 permits an operator to highlight selected regions ofdigitized preparatory images 254, specifying therein tissues to becryoablated. In the latter case, three-dimensional modeler 256 is thenuseable to translate regions highlighted on digitized preparatory images254 into equivalent regions of three dimensional model 258. In bothcases, tissues highlighted and selected to be cryoablated can bedisplayed by displayer 262 as part of integrated image 268, and can berecorded by memory 270 for future display or other uses.

[0224] Similarly, highlighter 280 is useable by an operator foridentifying tissues to be protected from damage during cryoablation.Typically, important functional organs not themselves involved inpathology may be in close proximity to tumors or other structures whosedestruction is desired. For example, in the case of cryoablation in aprostate, nerve bundles, the urethra, and the rectum may be in closeproximity to tissues whose cryoablation is desired. Thus, highlighter280 is useable by an operator to identify (i.e., to specify the locationof) such tissues and to mark them as requiring protection from damageduring cryoablation.

[0225] Preferably, interface 264 permits an operator to highlightselected regions of three dimensional model 258 so as to specify thereintissues to be protected from damage during cryoablation. Alternatively,interface 264 permits an operator to highlight selected regions ofdigitized preparatory images 254, specifying therein tissues to beprotected during cryoablation. In the latter case, three-dimensionalmodeler 256 is then useable to translate regions highlighted ondigitized preparatory images 254 into equivalent regions of threedimensional model 258. In both cases, tissues highlighted and selectedto be protected from damage during cryoablation can be displayed bydisplayer 262 as part of integrated image 268, and can be recorded bymemory 270 for future display or other uses.

[0226] Planning system 240 further optionally comprises a predictor 290,an evaluator 300, and a recommender 310.

[0227] Predictor 290 serves for predicting the effect on tissues of apatient, if a planned operation of cryoprobes 266 at theoperator-specified loci is actually carried out according to theoperator-specified operational parameters. Predictions generated bypredictor 290 may optionally be displayed by displayer 262 as part ofintegrated image 268, in the common virtual space of image 268.

[0228] In a preferred embodiment, predictions of predictor 290 are basedon several sources. The laws of physics, as pertaining to transfer ofheat, provide one predictive source. Methods of calculation well knownin the art may be used to calculate, with respect to any selected regionwithin three dimensional model 258, a predicted temperature, given knownlocations of cryoprobes 266 which are sources of cooling in proximity tosuch a region, known temperatures and cooling capacities of cryoprobes266, and a duration of time during which cryoprobes 266 are active incooling. Thus, a mathematical model based on known physical laws allowsto calculate a predicted temperature for any selected region withinmodel 258 under operator-specified conditions.

[0229] Experimentation and empirical observation in some cases indicatea need for modifications of a simple mathematical model based onphysical laws concerning the transfer of heat, as would be the case, forexample, in a tissue wherein cooling processes were modified by a highrate of blood flow. However, methods for adapting such a model to suchconditions are also well known in the art. Such methods take intoaccount heat dissipation in flowing systems, effected by the flow.

[0230] An additional basis for predictions of predictor 290 is that ofclinical observation over time. Table 1 provides an example of apredictive basis derived from clinical observation, relating tomedium-term and long-term effects of cryoablation procedures in aprostate. The example provided in Table 1 relates to treatment of BPH bycryoablation under a standardized set of cryoprobe operating parameters.TABLE 1 Predicted long-term effects of cryoablation Distance between 3week volume 3 months volume probes (mm) consumption (%) consumption (%)10 70 100  15 55 85 20 40 70 25 30 50

[0231] As may be seen from Table 1, clinical observation leads to theconclusion that reduction in the volume of a prostate followingcryoablation is a gradual process which continues progressively for anumber of weeks following a cryoablation procedure. The clinicallyderived information of Table 1, and similar clinically derivedinformation, can also serve as a basis for predictions generated bypredictor 290, and displayed by displayer 262 as part of integratedimage 268 in the common virtual space of image 268.

[0232] Evaluator 300 is useable to compare results predicted bypredictor 290 to goals of a surgical intervention as expressed by anoperator. In particular, evaluator 300 can be used to compareintervention results predicted by predictor 290 under a givenintervention plan specified by an operator, with that operator'sspecification of tissues to be cryoablated. Thus, an operator may useinterface 264 to specify tissues to be cryoablated, plan an interventionby using interface 264 to specify loci for insertion of cryoprobes 266and to specify a mode of operation of cryoprobes 266, and then utilizepredictor 290 and evaluator 300 to predict whether, under his specifiedintervention plan, his/her goal will be realized and all tissues desiredto be cryoablated will in fact be destroyed. Similarly, an operator mayutilize predictor 290 and evaluator 300 to predict whether, underhis/her specified intervention plan, tissues which he specified asrequiring protection from damage during cryoablation will in fact beendangered by his planned intervention.

[0233] Recommender 310 may use predictive capabilities of predictor 290and evaluator 300, or empirically based summaries of experimental andclinical data, or both, to produce recommendations for cryoablationtreatment.

[0234] As discussed above, predictor 290 and evaluator 300 can be usedto determine, for a given placement of a given number of cryoprobes andfor a given set of operating parameters, whether a planned cryoablationprocedure can be expected to be successful, success being defined asdestruction of tissues specified as needing to be destroyed, with nodamage or minimal damage to tissues specified as needing to be protectedduring cryoablation. Based on this capability, recommender 310 canutilize a variety of calculation techniques well known in the art toevaluate a plurality of competing cryoablation intervention strategiesand to express a preference for that strategy which is most successfulaccording to these criteria.

[0235] In particular, recommender 310 may consider several interventionstrategies proposed by an operator, and recommend the most successfulamong them. Alternatively, an operator might specify a partial set ofoperating parameters, and recommender 310 might then vary (progressivelyor randomly) additional operating parameters to find a ‘best fit’solution. For example, an operator might specify tissues to bedestroyed, tissues to be protected, and a two-dimensional array ofcryoprobes such as, for example, the two dimensional placement array ofcryoprobes determined by the use of guiding element 115 having a net ofapertures 120 shown in FIG. 8 hereinabove. Recommender 310 could thentest a multitude of options for displacements of a set of cryoprobes ina third (depth) dimension to determine the shallowest and deepestpenetration desirable for each cryoprobe. Recommender 310 could furtherbe used to calculate a temperature and duration of freezing appropriatefor each cryoprobe individually, or for all deployed cryoprobescontrolled in unison, in a manner designed to destroy all tissuesspecified to be destroyed, while maximizing protection of tissuesspecified to be protected.

[0236] Recommendation activity of recommender 310 may also be based onempirical data such as experimental results or clinical results. Table 2provides an example of a basis for making recommendations derived fromclinical observation. TABLE 2 Recommended number of cryoprobes to treatBPH American Urologists Number of Association cross-sectionsQuestionnaire with stricture of Prostate Number Score the Urethra Volumeof probes 0-7 1-3 25 2 0-7 1-3 40 2 0-7 2-5 40 2 0-7 1-3 50 2-3 0-7 2-550 2-3 0-7 1-3 60 2-3 0-7 2-5 60 3 0-7 2-5 100  4 8-19 1-3 40 2-3 8-192-5 40 2-3 8-19 1-3 50 2 8-19 2-5 50 2-3 8-19 1-3 60 3 8-19 2-5 60 3-48-19 2-5 100  4 20-35 1-3 40 3 20-35 2-5 40 3 20-35 1-3 50 4 20-35 2-550 20-35 1-3 60 4 20-35 2-5 60 5 20-35 2-5 100  6

[0237] Table 2 relates to the treatment of BPH by cryoablation. Table 2is essentially a table of expert opinion, wherein three criterion fordescribing the symptomatic state of a patient are related, by experts,to a recommendation for treatment. Table 2 was in fact compiled by agroup of experts in the practice of cryoablation utilizing a particulartool, specifically a tool similar to that described in FIG. 8hereinabove, yet a similar table may be constructed by other experts andfor other tools. Moreover, feedback from the collective clinicalexperience of a population of users of a particular tool may becollected over time, for example by a company marketing such a tool orby an independent research establishment, and such collected informationmay be fed back into recommender 310 to build a progressively betterinformed and increasingly useful and reliable recommendation system.

[0238] The first column of Table 2, the AUA score, is the score of aquestionaire in use by the American Urological Association which may befound in Tanagho E. A., and McAninich J. W., Smith's General Urology,published by McGraw-Hill, Chapter 23. The AUA score is an estimate ofseverity of symptoms as subjectively reported by a patient, and relatesto such urinary problems as incomplete emptying of the bladder,frequency of urination, intermittency, urgency, weak stream, straining,nocturia, and the patient's perceived quality of life as it relates tohis urinary problems.

[0239] The second and third columns of Table 2 relate to diagnosticcriteria discernable from three-dimensional model 258 or from digitizedpreparatory images 254 from which model 258 derives. The second columnis a measure of the length of that portion of the urethra observed to beconstricted by pressure from a patient's prostate. The third column is ameasure of the volume of that patient's prostate. Table 2 constitutes abasis for recommending an aspect of a cryoablation treatment for BPH,specifically for recommending, in column four, an appropriate number ofcryoprobes to be used in treating a specific patient, based on threequantitative evaluations of his condition constituted by the columnsone, two and three of Table 2.

[0240] Reference is now made to FIGS. 12a and 12 b, which is a flowchart showing a method for automatically generating a recommendationrelating to a cryoablation procedure, utilizing the information of Table2, or similar information, according to an embodiment of the presentinvention. In the specific example of FIGS. 12a-12 b, the generatedrecommendation is relevant to cryoablation of tissues of a prostate fortreatment of BPH.

[0241] At step 320 of FIG. 12a, first imaging modality 250 is used tocreate preparatory images, which are digitized at step 322 to becomedigitized preparatory images 254. In the example presented, images 254are cross sections of a prostate such as those generated by a series ofultrasound scans taken at regularly intervals of progressive penetrationinto the body of a patient, as might be produced by the ultrasoundequipment described with reference to FIGS. 8-10 hereinabove.

[0242] At optional step 324, an operator marks or otherwise indicates,with reference to images 254, locations of tissues to be cryoablated orto be protected, as explained hereinabove. At step 326 images 254 areinput to three-dimensional modeler 256, which creates three-dimensionalmodel 258 of the intervention site at step 328. Model 258, along withany operator-highlighted and classified regions of model 258, aredisplayed at step 329.

[0243] In a parallel process, raw materials for a recommendation aregathered. At step 330 clinical input in the form of an AUA score from aquestionnaire of a patient's symptoms is input. At step 332 a count ismade of the number of preparatory images 254 (cross-sections) of theurethra which show constriction to the urethra caused by pressure fromthe prostate tissue on the urethra. A count of cross-sections showingconstriction is here taken as an indication of the length of astricture. Determination of which cross-section images show signs ofconstriction may be made by an operator, or alternatively may be made byautomated analysis of images 256, using image interpretation techniqueswell known in the art. At step 334, information available tothree-dimension modeler 256 is used to automatically calculate thevolume of the prostate.

[0244] At step 336, information assembled at steps 330, 332, and 334 isused in a table-lookup operation to retrieve a recommendation for theappropriate number of probes to be used to treat the imaged specificcase of BPH.

[0245] At step 340, an operator optionally inputs specific boundaryconditions which serve to limit recommendations by the system. Utilizingmodel 254 created at step 328, operator-specified boundary conditionsfrom step 340, operator-specified identification of locations ofspecific tissues to be ablated or protected from step 324, and acalculated recommended number of probes from step 336, a recommendationfor optimal positioning of a recommended number of probes may be made atstep 342. Display of a recommended intervention is made at step 344.

[0246] Optionally, operator-specified placement of simulated cryoprobesmay modify or replace the recommended intervention, at step 346.

[0247] Step 344 is optionally iterative. That is, an operator mayrepeatedly modify definitions of tissues, boundary conditions, or manualplacement of simulated probes, until the operator is satisfied with thesimulated results. As a part of step 344, activities of evaluator 300may be evoked, so as to procure system feedback based on a simulatedintervention. Step 344 is repeated so long as desired by an operator,and until the operator is satisfied with the results.

[0248] Referring now to FIG. 12b which is a continuation of theflowchart of FIG. 12a, at step 348 a final plan is optionally saved to acomputer disk or other memory 270.

[0249] In optional step 350, details of the completed intervention plancan be used to estimate and display expected long-term results of theplanned intervention, such as an expected future volume and shape of theprostate. Information from Table 2 or an equivalent is utilized for step350, as indicated at step 352. It is noted that long-term volume of theprostate may also be treated as a boundary condition of an intervention,at step 340.

[0250] The example presented in FIGS. 12a and 12 b refers specificallyto a utilization of planning system 240 for treating a prostate for BPH.Similar utilizations may be contemplated, for treating other organs, orfor treating other conditions of a prostate.

[0251] In treating BPH, a desired goal is a reduction in prostate volumeso as to relieve pressure on the urethra of a patient, because pressureon the urethra from an enlarged prostate interferes with the process ofurination. In treating BPH there is no need to destroy all of a selectedvolume, but rather simply to destroy some desired percentage of thatvolume.

[0252] In treating, for example, a prostate tumor suspected ofmalignancy, goals of the intervention are quire different. To avoiddangerous proliferation of malignant cells, it is desirable to ablate adefined volume in its entirety. In such a context, when it is necessityto destroy all tissues within a selected volume, the functionality ofevaluator 300 of planning system 240 is particularly useful.

[0253] Evaluator 300 is able to calculate, for each arbitrarily selectedsmall volume of model 258, the cumulative cooling effect of allcryoprobes in proximity to said selected small volume. Consequentlyevaluator 300 is able to make at least a theoretical determination ofwhether, for a given deployment of cryoprobes utilized under a given setof operating parameters, total destruction of malignant tissues within aselected volume is to be expected.

[0254] Reference is now made to FIG. 13, which is a chart showingtemperature profiles for several cryoablation methods, useful forunderstanding FIGS. 14 and 15. FIG. 13 contrasts the temperatureprofiles for cryoablation used in prior art systems 354 as compared tothe temperature profiles 356 utilized according to the methods of FIGS.14 and 15.

[0255] Reference is now made to FIG. 14, which is a simplified flowchart of a method for ensuring total destruction of a selected volumewhile limiting damage to tissues outside that selected volume, accordingto an embodiment of the present invention.

[0256] The method presented by FIG. 14 comprises (a) deploying aplurality of cryoprobes in a dense array within a target volume, and (b)limiting cooling of the deployed cryoprobes to a temperature onlyslightly below a temperature ensuring complete destruction of tissues.The temperature profile required is shown in detail in FIG. 13, where itis contrasted to a temperature profile according to methods of priorart. According to the method of FIG. 14, limiting cooling of eachcryoprobe has the effect of limiting the destructive range of eachcooled cryoprobe. If a plurality of cryoprobes are deployed in ansufficiently dense array and cooled to an extent such as that indicatedin FIG. 13, a nearly-uniform cold field is created, the field beinguniformly below a temperature required to ensure destruction of tissueswithin the field, yet there is relatively little tendency fordestructive temperature to extend far beyond the deployed cryoprobearray. Thus, in contrast to methods of the prior art, the methodpresented by FIG. 14 relies on making a cryoprobe array more dense, andless cold. Control of degree of cooling may of course be accomplished bycontrolling a temperature of cryoprobes of the array, eitherindividually or collectively, or by controlling duration of cooling ofcryoprobes of the array, or both.

[0257] Reference is now made to FIG. 15, which is a simplified flowchart of another method for ensuring total destruction of a selectedvolume while limiting damage to tissues outside that selected volume,according to an embodiment of the present invention.

[0258] The method of FIG. 15 is similar to that of FIG. 14, in that itutilizes a dense array of cryoprobes cooled to a lesser extent than thecooling utilized according to methods of prior art. According to themethod of FIG. 15, however, cryoprobes at the periphery of a targetvolume are cooled less than are cryoprobes at the interior of the targetvolume. Cryoprobes at the interior of the target volume are, bydefinition, relatively distant from tissues desired to be protected,consequently they can be strongly cooled with impunity, thereby helpingto ensure total destruction of target tissues. In contrast, cryoprobesnear the surface of the target volume are closer to healthy tissues,consequently it is desirable to cool them less, so as to limit thedamage they cause. Such lesser cooling of surface cryoprobes ispossible, without sacrificing efficient destruction of target tissues,because a combination of weak cooling from surface probes together withstrong cooling from interior probes creates a near-uniform cold fieldnear the surface probes which ensures destruction of tissues on aninterior side of the surface probes, while causing relatively littledestruction of tissues on an exterior side of the surface probes.

[0259] Planning system 240 can be used effectively to plan dense arraysof cryoprobes according the method of FIG. 14 and of FIG. 15. Forexample, a user might specify a particular density of an array ofprobes, then use evaluator 300 to evaluate a range of possibletemperature and duration parameters to find an amount and duration ofcooling which ensures that the specified array will indeed create anearly-uniform cold field sufficient to destroy all target tissues.Alternatively, a user might specify a desired degree of cooling and useplanning system 240 to recommend a required density of the cryoprobearray.

[0260] Thus, evaluator 300 and recommender 310 can be used to calculatedplacement and operational parameters of cryoprobes in a manner whichguarantees a nearly-uniform cold field within a selected volume. Ifcryoprobes 266 are sufficiently small and placed sufficiently closetogether, cooling effects from a plurality of probes will influence eachselected small volume within a target volume, and an amount of requiredcooling can be calculated which will ensure that all of the targetvolume is cooled down to a temperature ensuring total destruction of thetarget volume.

[0261] In implementing the method of FIG. 15, control of degree ofcooling may of course be accomplished by controlling temperatures ofcryoprobes of the array, either individually or collectively, or bycontrolling duration of cooling of cryoprobes of the array, or both.

[0262] Reference is now made to FIG. 16, which is a simplified blockdiagram of a surgical facilitation system for facilitating a cryosurgeryablation procedure, according to an embodiment of the present invention.

[0263] In a preferred embodiment, a surgical facilitation system 350comprises a first imaging modality 250 and optional digitizer 252, forcreating digitized preparatory images 254 of an intervention site, afirst three-dimensional modeler 256 for creating a firstthree-dimensional model 258 of the intervention site based on digitizedpreparatory images 254, a second imaging modality 360 with optionalsecond digitizer 362 for creating a digitized real-time image 370 of atleast a portion of the intervention site during a cryosurgery procedure,and an images integrator 380 for integrating information fromthree-dimensional model 258 of the site and from real-time image 370 ofthe site in a common coordinate system 390, thereby producing anintegrated image 400 displayable by a display 260. Integrated image 400may be a two dimensional image 401 created by abstracting informationfrom a relevant plane of first three dimensional model 258 for combiningwith a real-time image 370 representing a view of that plane of thatportion of the site in real-time. Alternatively, a set of real-timeimages 370 may be used by a second three dimensional modeler 375 tocreate a second three dimensional model 402, enabling images integrator380 to express first three dimensional model 258 and second threedimensional model 402 in common coordinate system 390, preferably aCartesian coordinate system, thereby combining both images intointegrated image 400.

[0264] Various strategies may be used to facilitate combining of model258 (based on preparatory images 254) with real-time images 370 (ormodel 402 based thereupon, by images integrator 380. Processes ofscaling of images to a same scale, and of projection of a ‘slice’ of athree dimensional image to a chosen plane, are all well known in theart. Basic techniques for feature analysis of images are also wellknown, and can deal with problems of fine alignment of images from twosources, once common features or common directions have been identifiedin both images. Techniques useful for facilitating aligning of bothimages by images integrator 380 include: (a) identification of commonfeatures in both images by an operator, for example by identifyinglandmark features such as points of entrance of a urethra into, andpoints of exit of a urethra from, a prostate, (b) identification ofconstant basic directions, such as by assuring that a patient is in asimilar position (e.g., on his back) during both preparatory imaging andreal-time imaging, (c) operator-guided matching, through use ofinterface 264, of a first set of images, (d) use of proprioceptive toolsfor imaging, that is, tools capable of reporting, either mechanically orelectronically using an electronic sensor 364 and digital reportingmechanism 365, their own positions and movements, and (e) using a samebody of imaging equipment to effect both preparatory imaging, producingpreparatory images 254, and real-time imaging during a cryosurgeryprocedure, producing real-time images 370. For example, using ultrasoundprobe 130 of FIGS. 8-10 and FIG. 16 both for preparatory imaging and forreal-time imaging, and assuring that the patient is in a standardposition during both imaging procedures, greatly facilitates the task ofimages integrator 380. Equipping ultrasound probe 130 with stabilizer366 and controlling its movements with stepper motor 367, as shown inFIG. 16, yet further simplifies the task of images integrator 380.

[0265] It will be appreciated that the present invention can benefitfrom position tracking of various components thereof so as to assisteither in modeling and/or in actually controlling a cryoablationprocedure. Position tracking systems per se are well known in the artand may use any one of a plurality of approaches for the determinationof position in a two- or three-dimensional space as is defined by asystem-of-coordinates in two, three and up to six degrees-of-freedom.Some position tracking systems employ movable physical connections andappropriate movement monitoring devices (e.g., potentiometers) to keeptrack of positional changes. Thus, such systems, once zeroed, keep trackof position changes to thereby determine actual positions at all times.One example for such a position tracking system is an articulated arm.Other position tracking systems can be attached directly to an object inorder to monitor its position in space. An example of such a positiontracking system is an assortment of three triaxially (e.g.,co-orthogonally) oriented accelerometers which may be used to monitorthe positional changes of the object with respect to a space. A pair ofsuch assortments can be used to determine the position of the object insix-degrees of freedom.

[0266] Other position tracking systems re-determine a positionirrespective of previous positions, to keep track of positional changes.Such systems typically employ an array of receivers/transmitters whichare spread in known positions in a three-dimensional space andtransmitter(s)/receiver(s), respectively, which are in physicalconnection with the object whose position being monitored. Time basedtriangulation and/or phase shift triangulation are used in such cases toperiodically determine the position of the monitored object. Examples ofsuch a position tracking systems employed in a variety of contexts usingacoustic (e.g., ultrasound) electromagnetic radiation (e.g., infrared,radio frequency) or magnetic field and optical decoding are disclosedin, for example, U.S. Pat. Nos. 5,412,619; 6,083,170; 6,063,022;5,954,665; 5,840,025; 5,718,241; 5,713,946; 5,694,945; 5,568,809;5,546,951; 5,480,422 and 5,391,199, which are incorporated by referenceas if fully set forth herein.

[0267] Position tracking of any of the imaging modalities describedherein and/or other system components, such as the cryoprobesthemselves, and/or the patient, can be employed to facilitateimplementation of the present invention.

[0268] In a preferred embodiment, surgical facilitation system 350further comprises all functional units of planning system 240 asdescribed hereinabove. That is, facilitation system 350 optionallycomprises simulator 260 having user interface 264 with highlighter 280,each having parts, functions and capabilities as ascribed to themhereinabove with reference to FIG. 11 and elsewhere. In particular,system 350 includes the above-described interface useable by an operatorto specify placements and operational parameters of simulated cryoprobes256, and to specify tissues to be cryoablated or to be protected duringcryoablation.

[0269] Similarly, facilitation system 350 further optionally comprisesmemory 270, predictor 290, evaluator 300, and recommender 310, eachhaving parts, functions and capabilities as ascribed to them hereinabovewith reference to FIG. 11 and elsewhere.

[0270] Thus, in a preferred embodiment of the present invention,facilitation system 350 is able to undertake all activities describedhereinabove with respect to planning system 240. In addition,facilitation system 350 is able to provide a variety of additionalservices in displaying and evaluating at least one real-time image 370,and is further able to compare real-time images 370 to three dimensionalmodel 258, and also to compare information from real-time images 370 tostored information such as that identifying operator-specified tissuesto be cryoablated or to be protected, as is explained more fullyhereinbelow.

[0271] In a preferred embodiment, either first imaging modality 250and/or second imaging modality 360 may each independently be a magneticresonance imaging system (MRI), an ultrasound imaging system, acomputerized tomography imaging system (CT), some combination of thesesystems, or some similar system able to produce images of the internaltissues and structures of the body of a patient, yet in the case ofsecond imaging modality 360, ultrasound and MRI imaging are moretypically used, as being more conveniently combined with cryosurgeryprocesses.

[0272] Facilitation system 350 further comprises a first comparator 390,for comparing first three-dimensional model 248 with real-time image370, particularly to discern differences between both images. Suchdifferences constitute differences between a status of a plannedintervention and a status of an actual intervention in real-time. Tools,such as cryoprobes, tissues, such as a urethra, and ice-balls formedduring cryoablation, all figure as elements in three dimensional model258, and all may be visualized using second imaging modality 360. Thus,their expected positions, sizes, orientations, and behaviors may becompared to their actual real-time positions, sizes, orientations andbehaviors during cryoablation, by comparator 390.

[0273] Differences thereby revealed, and information concerning suchdifferences, can be of vital importance to an operator in guiding hisactions during an intervention, particularly if the operator deviatesfrom a planned intervention without being aware of doing so. Arepresentation of the revealed differences may be displayed by displayer262 and highlighted for greater visibility. A feedback mechanism 392,for example an auditory feedback mechanism, may be used to drawattention of an operator to serious discrepancies between a planned andan actual intervention.

[0274] Similarly, comparator 390 can be used to compare status ofobjects visible in real-time images 370 with stored information aboutoperator-specified tissues to be cryoablated. Comparator 390 can thusprovide information about, and displayer 262 can display, situations inwhich tissues intended to be cryoblated are in fact not effectivelybeing cryoablated by a procedure. Similarly, comparator 390 can be usedto check status of objects visible in real-time images 370, relatingthem to stored information about operator-specified tissues which are tobe protected during cryoablation. In the case of discrepancies betweenan actual situation and an operator-specified desirable situation,display 262 and feedback mechanism 392 can warn an operator when aprocedure seems to be endangering such tissues.

[0275] The capabilities of facilitation system 350 may extend yetfurther, to direct guidance to an operator in the manipulation ofcryoablation tools, and even to partial or complete control of suchtools during a phase of a cryoablation intervention.

[0276] Reference is now made to FIG. 17, which is a schematic diagram ofmechanisms for control of cryosurgical tools by a surgical facilitationsystem, according to an embodiment of the present invention.

[0277] A cryosurgical probe 50 is shown passing through an aperture 120in a guiding element 115 which is realized in this example as a plate110. As described hereinabove in the context of the discussion of FIGS.8-10, aperture 120 is for limiting sideways movement of probe 50, whichis however free to move forward and backwards towards and away from acryoablation site in a patient. In the prior art methods presented inFIGS. 8-10, such movement was conceived as under sole and exclusivecontrol of an operator who advanced and retracted probe 50 manually.

[0278] As has been noted above, the simulation, evaluation, andrecommendation capacities of planning system 240 and facilitation system350, based on preparatory images 254 and three dimensional model 258,allow system 350 to calculate a recommended maximum and minimum depthfor at which each cryoprobe 50 is to be used for cryoablation. Further,a cryoablation plan manually entered by an operator may also determine amaximum and minimum depth at which each cryoprobe 50 is to be used forcryoablation.

[0279] In a simple implementation of mechanical control based oninformation from planning system 240 or facilitation system 350, plannedmaximum and minimum depths generated by those systems are communicatedto an operator who adjusts a mechanical blocking element 430 accordingto a graduated distance scale 432, in a manner which limits forward orbackward movement of probe 50 so as to prevent an operator fromunintentionally and unknowingly advancing or retracting probe 50 beyondlimits of movement planned for probe 50. Such an arrangement guides andaids an operator in use and control of probe 50 for effectingcryoablation according to a plan.

[0280] In a somewhat more sophisticated implementation, control signals438 from system 350 activate a stepper motor 434 to directly controlmovement of probe 50. Thus, under control of system 350 and according toa planned, simulated, examined and theoretically tested procedure,stepper motor 434 can advance probe 50 to a planned depth for performingcryoablation. System 350 can also send temperature control signals toheating gas valve 440 and cooling gas valve 442, thereby controlling aflow of heating gas from heating gas reservoir 444 and a flow of coolinggas from cooling gas reservoir 446. Thus, under control of anintervention plan and utilizing mechanisms presented in FIG. 17, system350 is able to directly control some or all of a cryoablationintervention. Thus, in a typical portion of a cryoablation procedure,stepper 434 advances probe 50 a planned distance, cooling gas valve 442opens to allow passage of a gas which cools probe 50 to cryoablationtemperatures and maintains those temperatures for a planned length oftime, then cooling valve 442 closes to halt cooling. Optionally, heatinggas valve 440 then opens to allow passage of a gas which heats probe 50so as to melt tissues in contact with probe 50, thereby restoring to itfreedom of motion, whereupon stepper motor 434 can further advance orretract probe 50 to a new cryoablation position, at which new positionsystem 350 can optionally repeat this cryoablation process.

[0281] To ensure accuracy, movement of cryoprobe 50 may be monitored bya movement sensor 436. Moreover, all the facilities of system 350previously described, for comparing real-time positions of objects withplanned positions of those objects, can be brought to bear, to monitorthis independently controlled cryoablation process.

[0282] It is appreciated that certain features of the invention, whichare, for clarity, described in the context of separate embodiments, mayalso be provided in combination in a single embodiment. Conversely,various features of the invention, which are, for brevity, described inthe context of a single embodiment, may also be provided separately orin any suitable subcombination.

[0283] Although the invention has been described in conjunction withspecific embodiments thereof, it is evident that many alternatives,modifications and variations will be apparent to those skilled in theart. Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

What is claimed is:
 1. A planning system for planning a cryosurgicalablation procedure, comprising: (a) a first imaging modality forcreating digitized preparatory images of an intervention site; (b) athree-dimensional modeler for creating a three-dimensional model of saidintervention site based on said digitized preparatory images; and (c) asimulator for simulating a cryosurgical intervention, which comprises:(i) an interface useable by an operator for specifying loci forinsertion of cryoprobes and operational parameters for operation of saidcryoprobes for cryoablating tissues; and (ii) a displayer for displayingin a common virtual space an integrated image comprising a display ofsaid three-dimensional model of said intervention site and a virtualdisplay of cryoprobes inserted at said loci.
 2. The planning system ofclaim 1, further comprising a memory for storing said specified loci forinsertion of cryoprobes and said operational parameters for operation ofsaid cryoprobes.
 3. The planning system of claim 1, wherein said firstimaging modality is selected from the group consisting of magneticresonance imaging, ultrasound imaging and computerized tomographyimaging.
 4. The planning system of claim 1, wherein saidthree-dimensional model is expressible in a three-dimensional Cartesiancoordinate system.
 5. The planning system of claim 1, wherein saidinterface also serves for highlighting selected regions within saidthree-dimensional model.
 6. The planning system of claim 5, wherein saidintegrated image further comprises a display of an operator-highlightedregions.
 7. The planning system of claim 5, wherein said interface isuseable by an operator for identifying tissues to be cryoablated.
 8. Theplanning system of claim 7, wherein said integrated image furthercomprises a display of said operator-identified tissues to becryoablated.
 9. The planning system of claim 5, wherein said interfaceis useable by an operator for identifying tissues to be protected fromdamage during cryoablation.
 10. The planning system of claim 9, whereinsaid integrated image further comprises a display of saidoperator-identified tissues to be protected from damage during saidcryoablation.
 11. The system of claim 1, further comprising a predictorfor predicting an effect on tissues of the patient of operation of saidcryoprobes at said loci according to said operational parameters. 12.The system of claim 11, wherein said model displayer additionallydisplays in said common virtual space a representation of said predictedeffect.
 13. The system of claim 11, further comprising an evaluator forcomparing said predicted effect to an operator-defined goal of saidprocedure.
 14. The system of claim 13, wherein said evaluator is foridentifying areas of predicted less-than-total destruction of tissueswithin a volume of desired total destruction of tissues as defined by anoperator.
 15. The system of claim 13, wherein said evaluator is foridentifying areas specified as requiring protection during cryoablationwhich may be endangered by a specified planned cryoablation procedure.16. The system of claim 1, further comprising a recommender forrecommending cryosurgical procedures to an operator, said recommendationbeing based on goals of a cryoablation procedure, said goals beingspecified by said operator, and further being based on saidthree-dimensional model of said site, thereby facilitating planning thecryoablation procedure.
 17. The system of claim 16, wherein saidrecommender recommends an optimal number of cryoprobes for use in acryoablation procedure.
 18. The system of claim 16, wherein saidrecommender recommends an optimal temperature for a cryoprobe for use ina cryoablation procedure.
 19. The system of claim 16, wherein saidrecommender recommends an optimal duration of cooling for a cryoprobefor use in a cryoablation procedure.
 20. The system of claim 17, whereinsaid recommendation is based on a table of optimal interventions basedon expert recommendations.
 21. The system of claim 17, wherein saidrecommendation is based on a table of optimal interventions based oncompiled feedback from a plurality of operators.
 22. The system of claim17, wherein said recommendation comprises specific locations forinsertion of a cryoprobe to affect cryoablation.
 23. The system of claim16, wherein said recommended procedures are for cryoablation of tissuesof a prostate.
 24. The system of claim 23, wherein said recommendedprocedures are for treating BPH.
 25. The system of claim 23, whereinsaid recommended procedures are for treating BPH percutaneously.
 26. Thesystem of claim 25, wherein said recommended procedures are for treatingBPH transperineally.
 27. The system of claim 23, wherein saidrecommended procedures are for treating a mass.
 28. The system of claim27, wherein said recommended procedures are for treating a malignancy.29. The system of claim 24, wherein said table comprises a measure ofvolume of a prostate.
 30. The system of claim 24, wherein said tablecomprises a measure of length of a stricture of a urethra.
 31. Thesystem of claim 24, wherein said table comprises a measure ofsymptomatic severity of a BPH condition.
 32. The system of claim 31,wherein said measure of symptomatic severity of a BPH conditions is anAUA score.
 33. The system of claim 27, wherein said recommendation is ofmultiple cryoprobes closely placed so as to ensure a continuous coldfield sufficient to ensure complete destruction of tissues within atarget volume, while minimizing damage to tissues outside said targetvolume.
 34. A surgical facilitation system for facilitating acryosurgery ablation procedure, comprising: (a) a first imagingmodality, for creating digitized preparatory images of an interventionsite; (b) a three-dimensional modeler for creating a firstthree-dimensional model of said intervention site based on saiddigitized preparatory images; (c) a second imaging modality, forcreating a digitized real-time image of at least a portion of saidintervention site during a cryosurgery procedure; and (d) an imagesintegrator for integrating information from said three-dimensional modelof said site and from said real-time image of said site in a commoncoordinate system, thereby producing an integrated image.
 35. Thesurgical facilitation system of claim 34, further comprising a planningsystem according to claim
 1. 36. The surgical facilitation system ofclaim 34, further comprising a displayer for displaying said integratedimage in a common virtual space.
 37. The surgical facilitation system ofclaim 36, wherein said displayed integrated image is a two-dimensionalimage.
 38. The surgical facilitation system of claim 36, wherein saiddisplayed integrated image is a three-dimensional image.
 39. Thesurgical facilitation system of claim 34, further comprising athree-dimensional modeler for creating a second three-dimensional modelof at least a portion of said intervention site based on a plurality ofreal-time images.
 40. The surgical facilitation system of claim 39,wherein said images integrator is further operable for integratinginformation from said first three-dimensional model of said site andfrom said second three-dimensional model of at least a portion of saidsite in a common coordinate system.
 41. The surgical facilitation systemof claim 34, wherein said first imaging modality comprises at least oneof a group comprising magnetic resonance imaging, ultrasound imaging,and computerized tomography imaging.
 42. The surgical facilitationsystem of claim 34, wherein said second imaging modality comprises atleast one of a group comprising magnetic resonance imaging, ultrasoundimaging, and computerized tomography imaging.
 43. The surgicalfacilitation system of claim 42, wherein said second imaging modalitycomprises an imaging tool operable to report a position of said toolduring creation of said real-time image, thereby providing localizinginformation about said real-time image useable by said imagesintegrator.
 44. The surgical facilitation system of claim 43, whereinsaid imaging tool is an ultrasound probe inserted in the rectum of apatient and operable to report a distance of penetration in the rectumof the patient during creating of ultrasound images of a prostate of thepatient.
 45. The surgical facilitation system of claim 34, wherein saidfirst three-dimensional model is expressed in a three-dimensionalCartesian coordinate system.
 46. The surgical facilitation system ofclaim 36, further comprising an interface useable by an operator forhighlighting selected regions within said first three-dimensional model.47. The surgical facilitation system of claim 36, wherein saidintegrated image further comprises a display of an operator-highlightedregion.
 48. The surgical facilitation system of claim 36, wherein saidinterface is useable by an operator for identifying tissues to becryoablated.
 49. The surgical facilitation system of claim 48, whereinsaid integrated image further comprises a display of saidoperator-identified tissues to be cryoablated.
 50. The surgicalfacilitation system of claim 36, wherein said interface is useable by anoperator for identifying tissues to be protected from damage duringcryoablation.
 51. The surgical facilitation system of claim 50, whereinsaid integrated image further comprises a display of saidoperator-identified tissues to be protected from damage during saidcryoablation.
 52. The surgical facilitation system of claim 46, whereinsaid interface is useable by an operator for labeling topographicfeatures of said first three-dimensional model.
 53. The surgicalfacilitation system of claim 46, wherein said interface is useable by anoperator for labeling topographic features of said real-time images. 54.The surgical facilitation system of claim 46, wherein said interface isuseable by an operator for labeling topographic features of said secondthree-dimensional model.
 55. The surgical facilitation system of claimof claim 46, wherein said images integrator matches operator-labeledtopographic features of said first three-dimensional model withoperator-labeled features of said real-time images, to orient said firstthree-dimensional model and said real-time image with respect to saidcommon coordinate system.
 56. The surgical facilitation system of claimof claim 39, wherein said images integrator matches operator-labeledtopographic features of said first three-dimensional model withoperator-labeled features of said second three-dimensional model, toorient said first three-dimensional model and second three-dimensionalmodel with respect to said common coordinate system.
 57. The surgicalfacilitation system of claim 36, further comprising a simulator forsimulating a cryosurgical intervention, said simulator comprising aninterface useable by an operator during a planning phase of saidintervention, for specifying loci for insertion of cryoprobes andoperational parameters for operation of said cryoprobes for cryoablatingtissues, said image integrator being operable to integrate saidoperator-specified loci for insertion of cryoprobes into said integratedimage, and said displayer being operable to display said integratedimage.
 58. The surgical facilitation system of claim 36, furthercomprising a first comparator for comparing said first three-dimensionalmodel with said real-time image to determine differences arepresentation of said differences being further displayed by saiddisplayer in said integrated image.
 59. The surgical facilitation systemof claim 47, further comprising apparatus for providing feedback to anoperator regarding position of tools being used during a surgicalintervention as compared to said loci for insertion of cryoprobesspecified by an operator during said planning phase of saidintervention.
 60. The surgical facilitation system of claim 34, furthercomprising apparatus for providing feedback to an operator regardingposition of tools being used during a surgical intervention as comparedto operator-identified tissues to be cryoablated.
 61. The surgicalfacilitation system of claim 34, further comprising apparatus forproviding feedback to an operator regarding potion of tools being usedduring a surgical intervention as compared to operator-identifiedtissues to be protected during cryoablation.
 62. The surgicalfacilitation system of claim 57, further comprising apparatus forguiding an operator in the placement of cryoprobes for affectingcryoablation, said guiding being according to said loci for insertion ofcryoprobes specified by an operating during said planning phase of saidintervention.
 63. The surgical facilitation system of claim 47, furthercomprising an apparatus for limiting movements of a cryoprobes during acryoablation intervention according to said loci for insertion ofcryoprobes specified by an operator during said planning phase of saidintervention.
 64. The surgical facilitation system of claim 57, furthercomprising a cryoprobe displacement apparatus for moving at least onecryoprobe to at least one of said loci for insertion of cryoprobesspecified by an operating during said planning phase of saidintervention.
 65. The surgical facilitation system of claim 64, whereinsaid cryoprobe displacement apparatus comprises a stepper motor.
 66. Thesurgical facilitation system of claim 64, wherein said cryoprobedisplacement apparatus comprises a position sensor.
 67. The surgicalfacilitation system of claim 64, operable to affect cooling of said atleast one cryoprobe.
 68. The surgical facilitation system of claim 64,operable to affect heating of said at least one cryoprobe.
 69. Thesurgical facilitation system of claim 67, operable to affect scheduledmovement of said at least one cryoprobe coordinated with scheduledalternative heating and cooling of said at least one cryoprobe, toaffect cryoablation at a plurality of loci.
 70. A cryoablation methodfor ensuring complete destruction of tissues within a selected targetvolume while minimizing destruction of tissues outside said selectedtarget volume, comprising: (a) deploying a plurality of cryoprobes in adense array within said target volume; and (b) cooling said cryoprobesto affect cryoablation, while limiting said cooling to a temperatureonly slightly below a temperature ensuring complete destruction oftissues, thereby limiting destructive range of each cooled cryoprobe,said plurality of cryoprobes being deployed in an array sufficientlydense to ensure destruction of tissues within said target volume. 71.The cryoablation method of claim 70, further comprising utilizing aplanner for planning said dense array, said planner utilizing athree-dimensional model of said target volume to calculate a requireddensity of said dense array of deployed cryoprobes operated at aselected temperature, to affect complete destruction of tissues withinsaid selected target volume.
 72. The cryoablation method of claim 70,further comprising utilizing a planner for planning said dense array,said planner utilizing a three-dimensional model of said target volumeto calculate, for a plurality of cryoprobes deployed to a selected arrayof freezing loci, a temperature and duration of cooling for each of saidcryoprobes sufficient to affect complete destruction of tissues withinsaid selected target volume, while also minimizing cooling of tissuesoutside of said selected target volume.
 73. A cryoablation methodensuring complete destruction of tissues within a selected target volumewhile minimizing destruction of tissues outside said selected targetvolume, comprising: (a) utilizing cryoprobes to affect cryoablation at aplurality of freezing loci, said loci being of a first type and of asecond type, said first type being located adjacent to a surface of saidselected target volume and said second type being located at an interiorportion of said selected target volume; and (b) cooling cryoprobesdeployed at loci of said first type to a first degree of cooling andcooling cryoprobes deployed at loci of said second type to a seconddegree of cooling, said first degree of cooling being less cooling thansaid second degree of cooling, thereby affecting wide areas ofdestruction around each cryoprobe deployed at loci of said second typeand narrow areas of destruction around each cryoprobe deployed at lociof said first type, thereby ensuring complete destruction of tissueswithin a selected target volume while minimizing destruction of tissuesoutside said selected target volume.
 74. The cryoablation method ofclaim 73, wherein cryoprobes deployed to freezing loci of said firsttype are cooled to a first temperature and cryoprobes deployed tofreezing loci of said second type are cooled to a second temperature,said second temperature being lower than said first temperature.
 75. Thecryoablation method of claim 73, wherein cryoprobes deployed to freezingloci of said first type are cooled for a first length of time, andcryoprobes deployed to freezing loci of said second type are cooled fora second length of time, said second length of time being longer thansaid first length of time.
 76. The cryoablation method of claim 73,further comprising utilizing a planner for planning said dense array,said planner utilizing a three-dimensional model of said target volumeto calculate, for a given array of freezing loci, a required temperatureand length of cooling time for loci of said first type and for loci ofsaid second type, to affect complete destruction of tissues within saidselected target volume while minimizing destruction of issues outsidesaid selected target volume.
 77. A method for planning a cryosurgicalablation procedure, comprising: (a) utilizing a first imaging modalityto create digitized preparatory images of an intervention site; (b)utilizing a three-dimensional modeler to create a three-dimensionalmodel of said intervention site based on said digitized preparatoryimages; and (c) utilizing a simulator having an interface useable by anoperator for specifying loci for insertion of cryoprobes and forspecifying operational parameters for operation of said cryoprobes, tospecify loci for insertion of cryoprobes and operation parameters foroperation of said cryoprobes for cryoablating tissues; therebysimulating a planned cryosurgical ablation procedure.
 78. The method ofclaim 77, further comprising utilizing a displayer to display in acommon virtual space an integrated image comprising a display of saidthree-dimensional model of said intervention site and a virtual displayof cryoprobes inserted at said loci.
 79. The method of claim 77, furthercomprising utilizing a memory to store said specified loci for insertionof cryoprobes and said operational parameters for operation of saidcryoprobes.
 80. The method of claim 77, wherein said first imagingmodality is selected from the group consisting of magnetic resonanceimaging, ultrasound imaging and computerized tomography imaging.
 81. Themethod of claim 77, wherein said three-dimensional model is expressiblein a three-dimensional Cartesian coordinate system.
 82. The method ofclaim 77, further comprising utilizing said interface to highlightselected regions within said three-dimensional model.
 83. The method ofclaim 82, further comprising utilizing said interface to identifytissues to be cryoablated.
 84. The method of claim 78, wherein saidintegrated image comprises a display of said operator-identified tissuesto be cryoablated.
 85. The method of claim 82, further comprisingutilizing said interface to identify tissues to be protected from damageduring cryoablation.
 86. The method of claim 78, wherein said integratedimage comprises a display of operator-identified tissues to be protectedfrom damage during cryoablation.
 87. The method of claim 78, furthercomprising utilizing a predictor to predict an effect on tissues of thepatient of operation of said cryoprobes at said loci according to saidoperational parameters.
 88. The method of claim 87, wherein said modeldisplayer additionally displays in said common virtual space arepresentation of said predicted effect.
 89. The method of claim 87,further comprising utilizing an evaluator to compare said predictedeffect to an operator-defined goal of said procedure.
 90. The method ofclaim 89, further comprising utilizing said evaluator to identify areasof predicted less-than-total destruction of tissues within a volume ofdesired total destruction of tissues as defined by an operator.
 91. Themethod of claim 89, further comprising utilizing said evaluator toidentify areas specified as requiring protection during cryoablationwhich may be endangered by a specified planned cryoablation procedure.92. The method of claim 77, further comprising utilizing a recommenderfor recommending cryosurgical procedures, said recommendation beingbased on goals of a cryoablation procedure, said goals being specifiedby an operator, and further being based on said three-dimensional modelof said site.
 93. The method of claim 92, wherein said recommenderrecommends an optimal number of cryoprobes for use in a cryoablationprocedure.
 94. The method of claim 92, wherein said recommenderrecommends an optimal temperature for a cryoprobe for use in acryoablation procedure.
 95. The method of claim 92, wherein saidrecommender recommends an optimal duration of cooling for a cryoprobefor use in a cryoablation procedure.
 96. The method of claim 93, whereinsaid recommendation is based on a table of optimal interventions basedon expert recommendations.
 97. The method of claim 93, wherein saidrecommendation is based on a table of optimal interventions based oncompiled feedback from a plurality of operators.
 98. The method of claim93, wherein said recommendation comprises specific locations forinsertion of a cryoprobe to affect cryoablation.
 99. The method of claim92, wherein said recommended procedures are for cryoablation of tissuesof a prostate.
 100. The method of claim 99, wherein said recommendedprocedures are for treating BPH.
 101. The method of claim 99, whereinsaid recommended procedures are for treating BPH percutaneously. 102.The method of claim 101, wherein said recommended procedures are fortreating BPH transperineally.
 103. The method of claim 99, wherein saidrecommended procedures are for treating a mass.
 104. The method of claim103, wherein said recommended procedures are for treating a malignancy.105. The method of claim 100, wherein said table comprises a measure ofvolume of a prostate.
 106. The method of claim 100, wherein said tablecomprises a measure of length of a stricture of a urethra.
 107. Themethod of claim 100, wherein said table comprises a measure ofsymptomatic severity of a BPH condition.
 108. The method of claim 107,wherein said measure of symptomatic severity of a BPH condition is anAUA score.
 109. The method of claim 103, wherein said recommendation isof multiple cryoprobes closely placed so as to ensure a continuous coldfield sufficient to ensure complete destruction of tissues within atarget volume, while minimizing damage to tissues outside said targetvolume.
 110. A method for facilitating a cryosurgery ablation procedure,comprising: (a) utilizing a first imaging modality for creatingdigitized preparatory images of an intervention site; (b) utilizing athree-dimensional modeler for creating a first three-dimensional modelof said intervention site based on said digitized preparatory images;(c) utilizing a second imaging modality for creating a digitizedreal-time image of at least a portion of said intervention site during acryosurgery procedure; and (d) utilizing an images integrator forintegrating information from said three-dimensional model of said siteand from said real-time image of said site in a common coordinatesystem, thereby producing an integrated image said site, facilitative toan operator practicing a cryoablation procedure.
 111. The method ofclaim 110, further comprising utilizing a planning method according toclaim
 77. 112. The method of claim 110, further comprising utilizing adisplayer for displaying said integrated image in a common virtualspace.
 113. The method of claim 112, wherein said displayed integratedimage is a two-dimensional image.
 114. The method of claim 112, whereinsaid displayed integrated image is a three-dimensional image.
 115. Themethod of claim 110, further comprising utilizing a three-dimensionalmodeler for creating a second three-dimensional model of at least aportion of said intervention site based on a plurality of real-timeimages.
 116. The method of claim 115, further comprising utilizing saidimages integrator to integrate information from said firstthree-dimensional model of said site and from said secondthree-dimensional model of at least a portion of said site in a commoncoordinate system.
 117. The method of claim 110, wherein said firstimaging modality comprises at least one of a group comprising magneticresonance imaging, ultrasound imaging, and computerized tomographyimaging.
 118. The method of claim 110, wherein said second imagingmodality comprises at least one of a group comprising magnetic resonanceimaging, ultrasound imaging, and computerized tomography imaging. 119.The method of claim 118, further comprising utilizing an imaging tool toreport a position of said tool during creation of said real-time image,thereby providing localizing information about said real-time imageuseable by said images integrator.
 120. The method of claim 119, whereinsaid imaging tool is an ultrasound probe inserted in the rectum of apatient operated to report a distance of penetration of said tool in therectum of the patient during creation of ultrasound images of a prostateof the patient.
 121. The method of claim 110, wherein said firstthree-dimensional model is expressed in a three-dimensional Cartesiancoordinate system.
 122. The method of claim 112, further comprisingutilizing an interface to highlight selected regions within said firstthree-dimensional model.
 123. The method of claim 112, wherein saidintegrated image comprises a display of an operator-highlighted region.124. The method of claim 112, further comprising utilizing saidinterface for identifying tissues to be cryoablated.
 125. The method ofclaim 124, wherein said integrated image further comprises a display ofsaid operator-identified tissues to be cryoablated.
 126. The method ofclaim 112, further comprising utilizing said interface for identifyingtissues to be protected from damage during cryoablation.
 127. The methodof claim 124, wherein said integrated image further comprises a displayof said operator-identified tissues to be protected from damage duringsaid cryoablation.
 128. The method of claim 122, further comprisingutilizing said interface for labeling topographic features of said firstthree-dimensional model.
 129. The method of claim 122, furthercomprising utilizing said interface for labeling topographic features ofsaid real-time images.
 130. The method of claim 122, further comprisingutilizing said interface for labeling topographic features of saidsecond three-dimensional model.
 131. The method of claim 122, whereinsaid images integrator matches operator-labeled topographic features ofsaid first three-dimensional model with operator-labeled features ofsaid real-time images, to orient said first three-dimensional model andsaid real-time image with respect to said common coordinate system. 132.The method of claim of claim 115, wherein said images integrator matchesoperator-labeled topographic features of said first three-dimensionalmodel with operator-labeled features of said second three-dimensionalmodel, to orient said first three-dimensional model and secondthree-dimensional model with respect to said common coordinate system.133. The method of claim 112, further comprising simulating acryosurgical intervention by utilizing a simulator having an interface,and utilizing said interface during a planning phase of saidintervention to specify loci for insertion of cryoprobes into acryoablation site in a patient and to specify operational parameters foroperation of said cryoprobes for cryoablating tissues, and furtherutilizing said image integrator to integrate said specified loci intosaid integrated image, and utilizing said displayer to display saidintegrated image.
 134. The method of claim 112, further comprisingsimulating a cryosurgical intervention by receiving from an operatorduring a planning phase of said intervention specifications of loci forinsertion of cryoprobes into a cryoablation site and operationalparameters for operation of said cryoprobes for cryoablating tissues,utilizing said image integrator to integrate said operator-specifiedloci into said integrated image, and utilizing said displayer to displaysaid integrated image.
 135. The method of claim 112, further comprisingutilizing a first comparator for comparing said first three-dimensionalmodel with said real-time image to determine differences.
 136. Themethod of claim 133, further comprising utilizing apparatus forproviding feedback to an operator regarding position of tools being usedduring a surgical intervention as compared to said loci for insertion ofcryoprobes specified by an operator during said planning phase of saidintervention.
 137. The method of claim 133, further comprising providingfeedback to an operator regarding a position of a tool being used duringa surgical intervention as compared to said loci for insertion ofcryoprobes specified by an operator during said planning phase of saidintervention.
 138. The method of claim 110, further comprising utilizingapparatus for providing feedback to an operator regarding a position ofa tool being used during a surgical intervention as compared to aposition of operator-identified tissues to be cryoablated.
 139. Themethod of claim 110, further comprising utilizing apparatus forproviding feedback to an operator regarding a position of a tool beingused during a surgical intervention as compared to a position ofoperator-identified tissues to be protected during cryoablation. 140.The method of claim 133, further comprising utilizing apparatus forguiding an operator in the placement of cryoprobes for affectingcryoablation, said guiding being according to said loci for insertion ofcryoprobes specified by an operating during said planning phase of saidintervention.
 141. The method of claim 133, further comprising guidingan operator in the placement of cryoprobes for affecting cryoablation,said guiding being according to said loci for insertion of cryoprobesspecified by an operating during said planning phase of saidintervention.
 142. The method of claim 133, further comprising utilizingapparatus for limiting movement of a cryoprobe during a cryoablationintervention, said limitation being according to said loci for insertionof cryoprobes specified by an operating during said planning phase ofsaid intervention.
 143. The method of claim 133, further comprisingutilizing cryoprobe displacement apparatus for moving at least onecryoprobe to at least one of said loci for insertion of cryoprobesspecified by an operator during said planning phase of saidintervention.
 144. The method of claim 143, further comprising utilizinga stepper motor to move said cryoprobe.
 145. The method of claim 143,further comprising utilizing a position sensor to sense a position ofsaid cryoprobe.
 146. The method of claim 143, further comprisingutilizing control apparatus to control cooling of said at least onecryoprobe.
 147. The method of claim 143, further comprising utilizingcontrol apparatus to control heating of said at least one cryoprobe.148. The method of claim 146, further comprising controlling said atleast one cryoprobe according to a schedule of movements coordinatedwith a schedule of alternative heating and cooling of said at least onecryoprobe, to affect cryoablation at a plurality of loci.